When two or more independent mecha can combine to make another, larger mecha. It can be a decent way to hide a really big robot in plain sight, by breaking it up into pieces.
After the merge (accompanied by the stock Transformation Sequence), the new mecha will have powers and abilities greater than the sum of its parts. Combining Mecha are frequently a metaphor for Team Spirit and/or The Power of Friendship because of this.
It's common to find these in the same places as Transforming Mecha — indeed there are many that can do both. A frequent source of Technology Porn.
Who controls the combined form, and where the crew ends up after the merge, also varies. In some settings (such as Voltron) the crew remains in their separate individual cockpits (with the leader responsible for most of the robot's control), while other settings like Super Sentai and Power Rangers transfer the heroes to a central "bridge" area in the core of the mecha and they control the robot as a group (again, usually under the leader's direction).
In most cases each mecha comprises one specific piece of the resulting robot, with the group's leader (i.e. The Hero) forming the robot's head or torso in the process — after all, the leader is the 'head' of the group, so why not have them become the literal head of the combined form? This also eliminates the requirement for more than one Transformation Sequence, since the component mecha will always form the same result in the same manner. On the other hand, some mecha can mix-and-match their configurations to form any part of the combined robot, and it doesn't necessarily matter who forms which piece.
In many series, if a team of mecha is revealed to have a combined form, expect to see the individual mecha's abilities reduced to So Last Season status, with the mecha rarely used for anything other than their ability to combine. This is certainly the case with, for example, most Super Sentai and Power Rangers series, where once the team's Megazord is revealed (usually within the first couple of episodes, sometimes inside of the Pilot Episode), they will never use anything less. (Probably because hiring People in Rubber Suits to fight the Monster of the Week is a lot less expensive than the Stop Motion or CGI required to animate individual mecha doing the same.)
In cases where the mecha are sapient beings with no outside pilot (such as Transformers), the resulting personality of their combined form is frequently some manner of collective consciousness formed by the component members — this merged mind is often the result of whatever its component members can actually agree on, usually resulting in little more than a mechanized Dumb Muscle whose vocabulary consists primarily of one-syllable words and who can only focus on one task at a time: For the good guys, this creates a Gentle Giant; For the bad guys, this simply results in breaking and smashing stuff. Lots of stuff. And killing people, don't forget the killing.
In any case, it's often unclear where the necessary parts to operate this new robot came from — all the physical implausibilties of Transforming Mecha apply, to a greater degree.
More often than not, the legs-and-feet component of a combining robot is not as cleverly disguised as the other parts. It may appear as a giant, rectangular machine with obvious foot-shaped parts protruding from behind. In contrast, the head of the combining robot is almost always hidden in some sort of recess; in the Transformation Sequence, it usually emerges from said recess as a final step.
If the vehicle is a single thing to begin with but breaks apart to fight, you could be looking at Detachment Combat.
See Totem Pole Trench and The Worm that Walks for similar tropes involving living things.
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Super Sentai, and therefore Power Rangers, of course. 35 years of the former and 20 years of the latter with 2-3 super robots per season mean everything's been covered. Everything. For the purpose of simplicity, Power Rangers terms will primarily be used here - Super Sentai has few cross-series terms like 'zord,' without which this becomes a lot harder to describe.
To expand, the first Sentai, Himitsu Sentai Goranger, and its successor, JAKQ Dengekitai, never had mechas. It was on the third Sentai, Battle Fever J, that the series had a mecha (an idea taken from the Japanese tokusatsu Spider Man), and even that mecha wasn't a combining mecha. It was only until Sun Vulcan did they introduced the combining mecha idea. And even then, it was usually two or three machines combining - the eleventh series, Hikari Sentai Maskman, was the first to give each member a personal robot that shared his or her theme. "Great Five" was so named because it was the first robot to actually be made from five components.
The most common system is: each of the five Rangers has a Zord corresponding to whatever the series' general "theme" is. They combine into a humanoid Megazord, which handles the fighting for the early parts of the season when the villain decides to Make My Monster Grow. Then Sixth Ranger comes with his Mecha Expansion Pack which doubles the power of the ensemble. However, the variety of Zords mean there's no combining scheme we haven't seen.
Group of vehicles to giant robot? Pick a series, any series, with a vehicle theme, or the Super Sentai that predate the Zord-per-Ranger rule (the 2-3 Zords were usually a giant plane-thing and 1-2 giant ground vehicles.)
Group of humanoid robots to giant robot? This is perhaps the least-seen scheme, but it happens. The Shogun Zords were all humanoid and formed the Shogun Megazord, and the Turbo Rescuezords were like Transformers (vehicle-to-humanoid transformation) as well as being able to make a Rescue Megazord. Super Zeo Megazord and Titan Megazord even managed to have completely symmetrical formations rather than the Voltron-style one-on-each-side. You may choose to count the times Megazords combine into bigger Megazords, but it's rare for it to truly work that way (instead, the two Megazords' component Zords can recombine and make a larger formation.)
Group of animal robots to giant robot? Pick a series, any series, with an animal theme.
Group of vehicles to bigger vehicle? Rare, but a few Megazords have a vehicle mode as well as a robot mode. If the components are themselves vehicles, you get five Time Jets becoming the Time Force Megazord Jet Mode, or Operation Overdrive's Battle Fleet Carrier (whose components only exist in Stock Footage, sadly.)
Mix and Match? Time Force again. There's the speedy Mode Blue, the strong Mode Red, and the too-expensive-to-CGI-often Jet Mode, all with the same components. Also, Mystic Force has a dragon formation and a Megazord formation. The first two Megazords also had a tank mode and a robot mode.
Mecha Expansion Pack? More and more recent series have "auxiliary Zords" that can replace limbs to add new powers. Every year starting around 2000, both shows tend to feature a wide range of individual animals or vehicles who would start doing this with the base combined mecha. At times like this, instead of "GATTAI!" (combination), get used to "BUSOU!" (armament.) Once they acquire enough of these, they usually end up combining together to form a second complete mecha such as DaiTenkuu in Samurai Sentai Shinkenger/the Samurai Battlewing in Power Rangers Samurai; or the Dual Drive Megazord of Power Rangers Operation Overdrive (presented as a 'quick and dirty' emergency combination of the spare vehicles once too many of the usual vehicles had been damaged). Sometimes they all pile onto the main mecha at once. Also, some Sixth Ranger mecha do this with the combined robot of the other Rangers.
A rarer variant of this occurs when the Red Ranger's Zord can change into a humanoid robot, which then forms the Megazord by "wearing" the rest of the team's Zords as armor. So far there are only two examples: Gosei Sentai Dairanger's Dairenoh (AKA the Thunder Megazord) and Tokumei Sentai Go Busters's Go-BusterOh.
Combattler V and Voltes V (similar designs, from the same anime director). Combattler was the first such mecha to have a combination sequence that could actually be visibly followed (and as Bandai had become a sponsor, not coincidentally reproduced in toy form).
Zambot3: Zambot was formed by the combination of three vehicles: an aircraft, a tank and a terrestrial support vehicle.
Genesis of Aquarion has three fighter planes called Vectors combine into one huge robot with special abilities depending on which Vector forms the head. One forms the head, torso and arms, one forms the pelvis, legs and feet, and one forms a set of wings that attches where the abdomen would be.
Tidal Wave in Transformers Armada, who is composed of three ships called the Dark Fleet, that can also form a larger ship, and become a Mecha Expansion Pack Augment for Megatron.
The Big O episode 18 "The Greatest Villain". Simon Beck uses a megadeus that combines from three smaller vehicles.
Dai-Guard has a realistic take on this; at first, the titular mecha must originally be carted to the site and assembled from its component parts. It later receives an upgrade that allows the sections to move on their own and assemble the mech automatically; however, they are not equipped with weapons or anything else that does not serve simply to transport Dai-Guard, and must return to their "parts" form to assemble the machine.
Devastator from Transformers: Revenge of The Fallen. The individual vehicles may have had their own transformations (indeed, they were used to fill the Decepticons' ranks), but the transformation started as vehicles.
The Elebus and Simurgh combine into the Simurgh Splendid and Earthgain and Vyrose combine into Super Earthgain in Super Robot Wars 64.
In World of Warcraft, the fight against the boss Mimiron in the Ulduar dungeon goes through four distinct phases: the first against the Leviathan Mk. II (a miniature version of the tank fought as the first boss in the instance), second against the VX-001 Anti-Personnel Cannon (a turret with two guns on the side), and the third against the Aerial Command Unit (a helicopter). The * fourth* phase consists of fighting V0-L7R-0N, a combination of the three which looks like a giant mechagnome.
The Venture Brothers does have one legitimate (read: not made-up) Mecha, Jonas Venture Jr.'s Ventronic, which is most definitely a Voltron parody.
Also, During a Fake Action Prologue Similarly, we see Hank and Dean "Form up" (or to be more accurate, one sits on the others shoulders) in order to form "Mecha-Shiva".
Parodied in Robot Chicken with a sketch where Voltron's combination sequence takes an agonizingly long time to finish (as well as the group having to start over after messing up the sequence) while the monster proceeds to destroy the space station.
For those curious, it was the vehicle Voltron used in this sketch, which as its Japanese name (Dairugger XV) suggests, has over a dozen parts.
Another sketch has the evil giant monster challenge Voltron to a dance battle. And it was awesome.
Commander Keith: We just got served, team!
Multiple Transformers groups do this, most famously the Constructicons, who form Devastator. Generation 1 (Original) Devastator was formerly used as the picture for this page.
From the original G1 series alone there were the Constructicons (Devastator), Stunticons (Menasor), Combaticons (Bruticus), Predacons (Predaking), Terrorcons (Abominus), Seacons (Piranacon), Monster Pretenders (Monstructor), Aerialbots (Superion), Protectobots (Defensor), and Technobots (Computron). And that's not even counting the Japanese-exclusive teams (Trainbots, Multiforce...) or the subsequent series. Technically, the combiner teams could be classified as either "robots into mecha" or "vehicles into mecha", but since most of them had to transform into vehicle forms before combining, "vehicles into mecha" seems more accurate.
Aside from Tidal Wave, mentioned above, the truest example of this form in Transformers would be the Duocons: two vehicles (one land and one air in both cases) combining into a single robot, with no robot modes for the individual vehicles. The Autobot cassettes Raindance (cassette/jet-fighter) and Grand Slam (cassette/tank), who combine into the robot Slamdance, also count.
Transformers Animated is a special case regarding Transformers, as there was only one combiner robot, and he was formed from only two components: the Twins Jetfire and Jetstorm, who symmetrical dock to form Safeguard.
The movie Constructicons are a bit of a blurry case; explicitly, they only ever go from vehicle to combined mode on-screen, but other 'cons in the larger battle had the same vehicle designs - and individual robot modes. Meanwhile, the toyline isn't helping matters; the $100 "Supreme" Constructicon Devastator goes vehicles-to-Devastator with no individual robots, but it also has its own screen inaccuracies, like, for example, completely omitting one of the Constructicons. On the other hand, there's a set of all seven Constructicons available in the "EZ Collection" (Legends class; really small) class that can form both individual robots and a combined form. Word Of God is that Devastator is one robot who had to be split into seven (eight?) vehicles because nothing on Earth was big enough. There are others that don't technically qualify as Constructicons; it's just that their vehicle modes are coincidentally the exact same as Devastator's separate components.
Don't forget the movie Arcee: in the toyline, she is composed of three motorcycles that combine into one robot. The combined form was originally going to appear in the movie, but was ultimately cut.
Of particular note is the Power Core Combiners toyline, which features combining as its central gimmick. However, its combiners aren't what TF fans are used to; instead of five separate mechs, each combiner is composed of one mech and a number of drone vehicles that only transform for the sake of the combination.
Transformers is another series that gives us a number of types. Vehicles/beasts to robot, check. Humanoids combine, check - though if it doesn't involve a return to vehicle mode it's usually a two-bot combiner. Vehicles into vehicle, check - again, typically applies to two (Dreadwind and Darkwing become Dreadwing, which is a jet with no robot mode. Jetfire and Jetstorm combine one way to become Safeguard's robot mode or another to become Safeguard's jet mode.) Interchangeability, check. Expansion pack... many versions of Optimus Prime can combine with one other bot to become Optimus Prime [Something] Mode, so the story treats it that way, though the combinations are involved enough you'd think it was "two become new robot" rather than "Optimus is wearing Wing Saber" to look at them. RID's Omega Prime, though, is the only Optimus combo to be treated as not exactly either of his components. Heck, there's even a few really weird ones, like three vehicles/humanoid robots combining into weapons for larger robots to use (the Star Saber, Requiem Blaster, and Skyboom Shield from Transformers Armada), and a couple really off-the-wall instances of animals combining into a larger animal (Sky Lynx from G1 and Magmatron from Beast Wars Neo, the latter's organic beast modes resulting in a particularly bizarre combined alternate mode.) And then there's Six-Gun, made mostly from Metroplex's guns.
Parodied in Titan Maximum, down to the letter. (While they have shown the animation of the transformation sequence, most times they cut away to observers commenting on how long the transformation takes.)
Parodied in VH-1 Illustrated where George W. Bush suggests building 5 giant robots that can combine to form a even bigger robot to fight (fake) nuclear monsters.
One episode of Mighty Man featured a Humongous Mecha whose pieces were disguised as Chinese Ships (called Junk).
The Symmetrical Docking pairs in GaoGaiGar, and Big Volfogg in the same series.
The original Astro Boy manga (which predates Getter Robo by a good 20 years) had two of these. First there was Gadem, a group of 47 androids who combind to form a giant centipede (although he was later redesigned as a collection of magnetized gold particles in the remake) & one story even had Astro himself becoming part of a combiner made up of other humanoid robots in order to fight a giant snow leopard who was actually a combination of billions of electricity eating space amoebas.
Magic Knight Rayearth has a variation with its three Legendary Mashin (Rune Gods). The Mashin are Humongous Mechas that initially have the appearance of a dragon (Seles), a phoenix (Windam) and a lion (Rayearth). When the three spirits merge, the result is again a Humongous Mecha with all three Magic Knights inside.
In the second movie, Lagann-hen, After Lord Genome converts the Infinity Big-bang Storm after Tengen Toppa versions of the ENTIRE Dai Gurren-dan's ganmen appear (Kittan is the only one who died before this as the Mauve Shirts were spared in the movie. Nia also gets to use her own ganmen) they AGAIN combine to form the SUPER Tengen Toppa Gurren Lagann which resembles a body made of spiral power more than an actual mecha. Not just any body either - it's an enormous Kamina on fire with Simon's shades and the Tengen Toppa Gurren Lagann for a face.
They do this all the time. The Gurren-Lagann is the combination of Gurren and Lagann. Gurren-hen has this in Clipped Wing Angel form with the Dai Gun Doten Kaizan, a combination of the 4 Generals Flagships. It fires one volley of missiles, then gets promptly Giga Drilled.
Lagann's special ability is that it is able to fuse with other mecha. In fact, Gurren Lagann itself is a fusion of no less than six mechs: The three Gunmen that were combined into Gurren, Lagann, A bit of the Enkidu (Viral's Gunman- specifically the helmet), and a flying Gunman.
Lagann actually combines with several other mechs in the various incarnations of the show- for example, it fuses with what is eventually the Dai-Gurren during the Volcano battle, and in the Manga, Yoko fuses it with her own mecha.
BB Senshi Sangokuden uses demonic possession to explain the combining of living robots: Shiba-En's summoning of Shuu Neue Ziel leads the demon to grab him, both his brothers, and a robot-shaped artifact to form Senjin Gasshin Shuu Gundam.
BIONICLE sets had this as their earlier gimmick for you to buy all 6 sets, where you can combine three particular sets (although since they all shared the same template, any set could be subsituted for the "right" one you didnt have) into one giant "Kaita" model. Since they all looked like robots, it's safe to say they go for this trope. Also overlaps with Fusion Dance.
Xenogears, generally a Super Robot game, featured one combining mecha with Dominia and her compatriots.
This was later given a homage in the Xeno Saga games with Erde Kaiser. In Xeno Saga 1 and 2, Erde Kaiser was created from various parts which then combined into one big robot (in episode 1 the parts could actually be summoned in battle). In episode 3, Kaiser starts off already assembled.
In Ilivais X, prototypes Q through U combine to form STRUQ, which, in alphabetical order, are the head, body, legs, right cannon arm, and left blade arm. Though the individual mecha are very incompetent when in humanoid form, with the exception of Q.
Again, the Transformers combiner teams, as listed above. Depending on the series and combination, though, the process isn't perfect, as it turns out creating a single composite mind from five or more very different robots isn't exactly easy.
Energon has this as the main gimmick for the Autobots. Just about any two Autobots were capable of combining with one another, with one forming the upper body and the other forming the lower body. Whoever was the top half was the one in control of the combination.
Mighty Orbots is a combination of types: the components are independent robots, but their human leader and his assistant enter inside, as their craft becomes the united form's control room. Once achieved, the pair control the movements of the united form, while the robots operate their specific internal functions at the command of their leader.
"Sym-Bionic Titan" has the main characters form the titular Titan by connecting their 2 sets of humanoid armor, plus the autonomous robot Octus, to form an actual humanoid robot.
Legion Of Superheroes has possibly the ultimate example: after his Face Heel Turn, Brainiac 5 takes control of his entire species—composed of metamorphing robots linked in a Hive Mind—and when challenged by the Legion, turns all of them into a single gigantic battlebot.
Digimon Xros Wars has this as its core gimmick setting it apart from the preceding Digimon series, referring to the combining process as DigiXrossing. A majority of component Digimon don't look robotic (nor do most of the resulting combinations beyond the main characters), but the combined forms of lead Digimon Shoutmon were clearly designed with classic combining mecha styles in mind.
Genesic GaoGaiGar. A dolphin, shark, two moles and a bird thing were substituted for the vehicles, going the opposite way from GaoFighGar.
Gun X Sword has the El Dorado V. Despite being crewed by senior citizens, it easily surpasses all other examples on this list when it comes to being fueled by hot blood.
Dancougar probably has the most extreme version of this. Each of the robots can transform between animal, vehicle AND humanoid forms, and they can all combine into a giant robot.
* Magmatron, of the Japanese-only Transformers series "Beast Wars Neo". Unlike most of the examples from Transformers, Magmatron was actually one individual that could separate his body into three smaller dinosaurs. The dinosaurs could also combine to form a bigger dinosaur with three heads.
The central premise of the anime Zoids: Fuzors.
The non-canon Beast◊ of the Transformers comics, formed by the Dinobots. TFwiki put it best when they said "This is a monument to all your sins."
The Beast Wars toyline featured Magnaboss, a combiner made of an elephant, an eagle, and a lion, each with an individual robot mode, and Tripredacus, who was similarly composed of a cicada, a lobster, and a beetle. The three components of Tripredacus appeared briefly on the cartoon, though they looked nothing like their toys because of budget constraints.
There were some animal combiners in G1, too, with Predaking being the best known.
Six of the Pink Elephants from Dumbo actually combine into a large monster made entirely out of Pink Elephant heads during the song "Pink Elephants on Parade."
The Legioss and Tread fighters from Genesis Climber Mospeada could merge into a bigger aircraft, and each could independently become a robot.
The Thunderbirds in the anime remake (2086) which actually made some sort of sense. It's quicker to move the smaller vehicles by strapping them to the sides of the heavy lifter than to send them all independently.
The 15 "small" vehicles of Dairugger XV (the "other" Voltron series) could not only combine into one gigantic robot, but also combine (in three specific groups of five) into three larger vehicles.
Each unit in the Brave SeriesThe Brave Express Might Gaine had a train form. Each of the different "teams" (Might Gaine, Might Kaiser, the Bombers, and the Divers) were also capable of taking on a combined train form, which, along with Might Gunner's train form, could lock together to perform their ultimate (and sadly, only used once) Finishing Move, the Joint Dragon Fire. Given the fact that the hero of the series is a teenage train magnate, this is about as surprising as finding sand in the Sahara Desert.
The titular vehicle in Supercar Gattiger is formed by combining its five component cars — the Center Machine, Left Machine, Right Machine, End Machine, and Back Machine.
In the Xbox 360 freeware title Aegis Wing, when two or more player ships come within a certain range of each other (you can tell because a line of dots show up with a blue X in the middle), a player can press X to flip and connect to the other guy. The one who initiated the merge becomes an omnidirectional gun turret, while the mergee steers and fires the forward gun.
Two Player Mode in Blasteroids can have one player with a ship in Speeder mode (small, fast and maneuverable with little armor or firepower in exchange) combine with the other's ship in Warrior mode (large, slow but heavily armored) to form the Starlet: The Speeder becomes a player-controlled turret that has firepower increased for its role, while the Warrior body of the Starlet loses its firepower but gains maneuverability in exchange.
In Wing Commander: Prophecy one common enemy fighter is the skate. They are able to form a "cluster", capable of laying mines, launching torpedos, and carrying out bombing runs with a cannon that can damage capital ship components. Needless to say, it's safest to knock apart any clusters and destroy the individual ships before they can combine.
Star Force has an enemy like this called Larios, which is a core that summons other fortresses to combine with it. Destroying the core before the fortresses combine with it is worth a bonus 50,000 points.
In Dogyuun, player 1 can fuse with player 2 to combine into a larger plane. This allows the players to get massive firepower, but it also comes with a price- if it gets hit, both players lose a life.
A small handful of Transformers combine into larger alt modes instead of larger robot modes. Dreadwing is probably the best example. Of course, they all had their own robot modes anyhow... save for Tidal Wave, who was a big robot, a big ship, or three small ships.
The concept was parodied in an episode of Reboot when the characters piloting the individual animal-mechs (in this case, insects) first couldn't figure out how they were supposed to arrange themselves to form the giant robot, and then when they did, the resulting robot looked nothing at all like it had been formed from the components that made it up.
Mix and Match
Several combinations, each of which has a distinct merged form.
Anime and Manga
Vandread: A different merged form for each girl's Dread fighter when joined with Hibiki's Vanguard mecha, plus one big gestalt robot with all four. Usually the combinations were metaphors for sex, with Hibiki's robot merging with a female's fighter and the sum being greater than the parts. The operators would sit in positions indicative of the relationships. However, for the final form involving a male, three women, a malfunctioning robot, and an alien lifeform (praxis) all lumped together, perhaps the writers dodged the orgy metaphor and went with something like friends working together to save the day.
Getter Robo. The first combiner robot, with three separate combinations depending on the order of its three component vehicles.
The same idea was taken further with Lightspeed Electrogod Albegas (the "lost Voltron" — plans to be incorporate it as a third chapter were scrapped, but Voltron-branded toys were still distributed in America); its three component robots had six combinations.
X-Head Cannon, Y-Dragon Head, and Z-Metal Tank from Yu-Gi-Oh! can each combine with one other of those three to create XY-Dragon Cannon, XZ-Tank Cannon, or YZ-Tank Dragon. Or, they can all combine together to create XYZ-Dragon Cannon. In Yu-Gi-Oh! GX, V-Tiger Jet and W-Wing Catapult were added: these could combine with each other to form VW-Tiger Catapult. That could then combine with XYZ-Dragon Cannon to form VWXYZ-Dragon Catapult Cannon, the most blatant version of this trope in Yu-Gi-Oh. GX also features Assault Cannon Beetle, a monster which uses an identical set-up to XYZ.
Ground Control 2 has the alein race using bio-technology, allowing them to combine to form totally diffrent units.
Ganbare Goemon 3 had the Big Bad, Jurokubei, use a huge lion mech flanked by two small snake mechs, eventually the lion would become a torso with head and legs while the snakes became the arms, creating a giant samurai robot. It then glides up to Impact, drawing it's swords threateningly... then the incompetent cross-dressing second in command, Bismaru, flies in his nun-head escape pod and lands right on top of the enemy mech, offering no benefit at all and making it look plain ridicuous. Jurokubei is left wailing about how Bismaru ruined his big scene.
The Seacons, Generation 1 Transformers latecomers, used the usual "four limbs plus the commander as torso" combination, but actually had six members; whichever subordinate was left out could transform into a gun for the combined form.
The aforementioned "four limbs plus the commander as torso" configuration was actually used for several combiners starting in the second season of G1—called the "Scramble City" combiners after a Japan-onlyOVA that heavily involved them and showed off the limb-switching gimmick. They were originally the Aerialbots/Superion, the Protectobots/Defensor, the Stunticons/Menasor, and the Combaticons/Bruticus, and season three would add the Technobots/Computron and the Terrorcons/Abominus. They could use the four smaller robots as limbs completely interchangeably—even switching arms/legs between teams (at least with the toys). Behold Abomenaticus! (Takes parts from Abominus, Menasor, and Bruticus.)
And in Transformers Energon, there were three combiners that worked like this, named in homage to G1 combiners: Superion Maximus, Bruticus Maximus, and Constructicon Maximus. They couldn't interact with the G1 toys but they could interact with each other in the same ways that the G1 Scramble City combiners could. In a similar vein, almost every Autobot in Energon had the Spark of Combination; any two Autobots of similar size with this ability could combine into a (slightly) larger robot.
The toys even represented this with a more one-size-fits-all transformation, as each Autobot could turn into the legs or the torso. The potential combinations were many - far more than the show could feature.
The Japanese-exclusive Multiforce also did this. They could also all combine into a single large robot.
Of course, since Ruination was a redecoed G1 Bruticus, this should not be surprising.
Transformers likes this. A sub-line called the Micromaster Combiners consists of pairs of robots who combine to form single vehicles. Though each had a specific partner, one of the selling points was that any two Micromaster Combiners could combine, even if the resulting vehicle was... unconventional◊. Or, for that matter, outright insane◊.
This was later played on and deconstructed in the second film. Skids and Mudflap have the combined form of a 1930's ice-cream truck. However, during the opening chase scene, they take a corner too sharply, split apart, and careen into a wall.
Mecha Expansion Pack Augment
A smaller mecha simply attaches to a larger one, usually as a weapon or a bit of armor.
Anime and Manga
Mazinger Z is the first example - the robot is powered by dropping a small aircraft (the "pilder") onto its head. And then it is combined with a Jet Pack to allow it fly.
Viral: How is he suddenly able to power up like this?! All he did was tack on the mini-Ganmen!!
However it's subverted/parodied in one instance of the manga, when Kamina decides combining them the same way every time isn't "artistic" and tries to form "the Lagann-Gurren".
There's actually a subtle, and really bad pun in that Simon, whose name is based on below is on the top and Kamina whose name roughly means above (it's a series thing; everyone lives underground), is on the bottom of the Gurren Lagann combination. Told you it was a bad pun.
You all forgot to mention when the Chouginga Gurren Lagann combines with the hotblood of the Dai-Gurren Brigade to form the mech the series was named after. The resulting combination erupts through the center of a galaxy it stands on top of, is constantly on fire, and has like 13 heads, including one IN THE MOUTH OF ANOTHER.
Most notable: Gundam ZZ's titular Gundam was formed by 3 fighters, and Gundam SEED Destiny had the Impulse which was made up by variable fighter jets. In Gundam 00 the titular Gundam can also be powered up by enabling the 0 Raiser as a kind of attached catalyzer.
Victory Gundam had not only the titular Gundam as a combination of three fighters, but some of the atmopheric mobile suits had an upper torso that could turn into a helicopter, and a seperate "leg unit" that followed the cockpit around which would be attached to make a full mobile suit.
In some sort of weird variation of this, the S-Gundam from Gundam Sentinel has the components and trappings of a Combining Mecha, including separate cockpits, but is usually piloted by one human pilot and a very advanced AI.
The Brave Series (which GaoGaiGar hails from) does this with incredible frequency. Every single series has the main hero mecha combine with at least one larger support vehicle to form his main "super" robot mode. This form then almost always mid series gets a second robot who combines with it as well to form a "Great" form. Additionally, one of the secondary mecha teams usually gets an extra member (who becomes additional armor and weapons). From Brave Express Might Gaine onwards, there is also typically one mecha in the series who forms a weapon for the main robot. Usually this is a gigantic cannon, but on some occasions, it takes the form of a huge sword or the legendary Goldion Hammer in Gao Gai Gar.
GaoGaiGar, where several vehicles combine with a central lion-robot to make it larger and more powerful. (Original only - later versions from FINAL replaced the core or the peripherals.)
Oddly on its first appearance they were still working on some of the sequence and it ended up banging the parts up pretty badly.
Gravion, likewise has four vehicles combining with a central bot.
In Gravion Zwei, the second season, there is a second mecha with also four vehicles upgrading the central bot. The vehicles cas be swapped between the two bots, and one of the bots can be upgraded by the eight vehicles and the other bot.
In Dennou Coil, Satchii and its copies can dispatch spherical patrol units, equipped with beam weapons. These can be re-assembled into pre-allocated slots, enabling the base unit to fire them all at once. Satchii differs from the other examples by being purely virtual, but since most of the show's characters dwell in cyberspace it is still considered a major threat.
Blocker Gundan IV Machine Blaster combined the concept of Mazinger Z with Super Sentai - instead of one robot with a piloted aircraft that would attach to it, there was a team of four, each robot with its own piloted aircraft that formed the robot's head.
The Magnemite, Beldum, and Klink lines from Pokémon actually do this to evolve.
The Huckebein MK III in Super Robot Wars could combine with the R-Sword into the Huckebein Boxer, or be combined with the AM Gunner ship to form the Huckebein Gunner.
SRX also had an addon in the form of the R-Gun, a mecha whose main purpose is to transform into a huge gun. It was decent on its own, but could perform the ridiculously powerful Heaven And Earth One Shot Sure Kill Cannon combo attack with SRX, an attack so powerful that in at least one game, it could kill the final boss in one shot.
Rush and Treble to Classic Mega Man and Bass, respectively.
An Awesome, but Impractical example of this is Nod Avatar Warmech from Command & Conquer 3. It would literally rip pieces off of allied vehicles to upgrade itself; in the end you could have an invisible Giant Robot with dual lasers, with a flamethrower and stealth detectors for good measure. This is somewhat worse that it sounds, since not only do you have to sacrifice a unit for every Avatar you upgrade, it takes time and micromanagement away from a better purpose (like using your tanks AND Avatars to crush your enemies). It could be somewhat useful, however, if your opponent is also Nod, because you could make your Avatar stronger and instantly destroy their vehicles.
It's strong armor does make up for the traditional NOD weakness where their tools can dish out the pain but can't take it. Of course multiplayer is too fast paced to ever get the upgrades done but in the campaigns you can just turtle up untill you are ready to unleash the unstoppable mecha goodness.
In Xenogears, Jessiah's Buntline Gear transforms into a mecha-sized handgun for his son's Renmazuo... with the cockpit as the bullet.
Hey, he made sure to fix that little design flaw before he piloted it.
The Sturmvogel from Einhander. Once you damage the main body enough, it calls in an armored unit to attach on top, starting the second part of the boss fight.
To confuse the matter, several Mini-con teams could combine into something larger - Perceptor was the mean three Minicons combined into a robot, but other teams could combine into Transformer-sized weapons; the Star Saber, Skyboom Shield and Requiem Blaster.
Also in Transformers Armada, Optimus Prime's combinations with Jetfire and Overload (sometimes at the same time) and Megatron's combination with Tidal Wave were exactly this. This also showed up in several other series:
Megatron is usually thought to be unable to fire on his own, but he is seen firing himself in the opening sequence and once ever in show, suggesting he can when he really, really wants to. Maybe it's aiming that's the problem.
The Headmasters, Targetmasters, and Powermasters, in which mobile suits for human(oid) partners became the heads, weapons, or engines for larger Transformers, respectively.
In the Japanese post-G1 sequels, Headmasters were smaller Cybertronians from the planet Master linking up with giant non-sentient robot suits called Transtectors (basically, think of the cartoon version of Scorponok and Fortress Maximus. The larger robots that Zarak and Spike/Cerebros combine with would be called Transtectors in Japan.) Powermasters were called Godmasters and were humans in mobile suits*
and a transformation call.]] linking with Transtectors. Headmaster Juniors were also suited human sidekicks linked with Transtectors. Targetmasters were Master robots partnered with real, living Transformers.
The 1989 Japan-only line of Zoids had Shoteagle, Gorgolauncher, and Thundercannon which plugged into larger "grade up" types after transforming into a BFG.
Parodied in One Piece, where, to fight the massive zombie Oars, Franky, Chopper, Usopp, Zoro and Sanji "combine" (really just stand on each other) into a massive humanoid figure dubbed "Big Emperor". It didn't do anything besides add extra comedic value, because Robin refused to "dock in" as the left arm, claiming that it would be "too embarrassing".
In One Piece: Unlimited Cruise 2, they do this again, with Luffy and Brook joining in.
And then there's Chapter 636, where they play the trope completely straight, with the Black RhinoFR-U #4 combining with BrachioTank #5 to form the humanoid "Iron Pirate Franky Shogun".
At least, One Piece protagonists are physically strong enough to "combine". Normal people, on the other hand... courtesy of Sluggy Freelance, see here.
Similary done in the LIVE-ACTION Hong Kong film Holy Weapon (1993). The Seven Virgins are played by some of Hong Kong's most famous actresses. And they actually fight. Don't miss it!
Getter Robo is the ultimate example of Combining Mecha as it is capable of combining with absolutely anything, mechanical or not and transforming them into mecha. This has included living people, nuclear missiles, THE DINOSAURS, Mars and other planets and eventually an entire freakin' GALAXY.
The Scavengers team from GUNNM: Last Order ended up being cannon fodder when Toji just punche the crap out of them once they combine like Voltron with a series of Electromagnetically accelerated punches. To make it even worse, their appearance did not last 2 panels.
IIRC, ARMD I and II were supposed to link to the Macross anyway, but the Zentradi prevented them from achieving this in the series. And then when the Macross used the Fold system they took along the Daedalus and Prometheus (killing the crews of both ships in the process) and so had no choice but to use them instead. They needed the defensive weaponry and runways provided by the two ships.
Not sure where else to put it, since the characters are both the pilots and somewhat their own Mecha. Anime only MÄR characters, the Flat Sisters: Grave, Allegro and Moderato form Rotkappchen Waltzer, what looks like a giant rag doll.
Which was probably the inspiration for the Headmasters of various Transformers series, which were people in special Powered Armor that lets them turn into the head of a Transformer to make it stronger.
There's also Targetmasters (gun) and Powermasters (engine.)
The Machine Emperors from Yu-Gi-Oh! 5Ds, made up of five different types of monster cards ('Core', 'Top', 'Guard', 'Attack', and 'Carrier'). The 'Wisel' cards form a giant humanoid, the 'Skiel' cards form a giant bird, and there's supposedly a third set which has yet to be revealed. They can be powered up by using stronger versions of the individual cards. They can even be mixed between two different creatures, i.e. creating Wisel with a Skiel Carrier card produces a Wisel with wings where it's legs should be.
As of episode 110, the 3rd Machine Emperor, Grannel, has been revealed, taking the appearance of a giant gold golem-like creature.
It has the form of a tank, with a cannon.
Mirai Robo Daltanious, which was originally intended to Voltron, involves a combination of a humanoid robot, a lion, and a vehicle - the same types of mecha used by Albegas, Golion, and Dairugger, the shows that did become Voltron.
In the two-part Kid Icarus short "Palutena's Revolting Dinner" from Studio Shaft, the vegetables (brought to life thanks to a rejuvination potion) fuse together to form a giant vegetable creature.
In the sequel, he has a version of it built for himself in the event that he's ever staring down a giant robot.
This was the main gimmick of the CapcomShoot 'em UpSide Arms: by picking a certain power-up, one player could combine their mecha with the other player's to form a more powerful mecha controlled by both.
As an April Fool's Day joke, Blizzard showcased a new unit for the Terrans: The Terra-tron, which is formed by combining ALL OF THE BUILDINGS IN THE AREA into a hugemecha. It is loaded with shout-outs to other famous uses of this trope, just listen to its dialogue.
Both parodied and played straight in Operator: After forcibly combining his opponents' mech with his own [unusually, an irreversible process that forced the other guy to abandon ship], Griff later has a dream about 'combining' that is a direct Shout Out to Gurren Lagann
Megas XLR has animal-to-robot ones that were damaged when Coop uses them as impromptu augmentation for Megas. This shows why they must be designed for that purpose, as he more or less just crammed his arms and legs up their mecha asses, and wrecked them so heavily as to drive one of the pilots to tears and elicit shock from the Evil Overlord: "I thought I was evil. That's just mean." Though ironically, it still manages to give Megas the needed power boost to defeat said Evil Overlord.
As another example from the same series, in the first episode (and the Lowbrow pilot), five Glorft robots combine into a giant humanoid mecha... and six of those mecha combine into an even bigger mecha, with Gorrath's spider-like mecha forming the head. It's as ridiculous as it sounds.
Joe and his wheelchair buddies from Family Guy apparently have the power to form Crippletron, and unlike the other parody examples, the thing actually works.
In the fight on Celebrity Deathmatch between n* Sync and The Backstreet Boys, each boy band had a combiner form they used in the ring.
Actually The Backstreet Boys were the only ones to form one. It was called the "Backstreet Beast"
n*Sync did form some spinning rotor-like object that had their toenails as blades
In The Venture Brothers, the Venture twins' overactive imagination during a witness testimony in a court case against the Monarch culminates in them combining together to form "Mecha Shiva", which they reenact in the court room.
Anubian in Huntik is a monster that acts like a Combining Mecha. Five flying bug-eyeball-things combine with a torso to create the creature.
Dexters Laboratory has a parody of this in one episode - all of Dexter's family members control a different section of the combined robot, and thus are out of sync until they figure out how to work together. In fact, they even have to switch places early on because they had no idea how to properly use the individual limbs.
Adventure Time did this with the Body parts people that the Magic Man created.