Taiki has some mock posters of Toei's Tokusatsu characters in his room. The most distinct one looks like Kamen Rider Double, the then-current Kamen Rider series. Funnily, Riku Sanjo writes both this series and Double.
He also has posters of Kamen Rider OOO and Kamen Rider Fourze throughout the rest of the series (and Hunters), making Shoutmon's Rider-inspired scarf in the third arc all the more fitting.
And of course, then there's the first scene of episode one, where Taiki has a dream where he and the boys are backed up by Digimon from all five previous seasons.
The three main components of Shoutmon X3 are pretty much a semblance to Getter Robo pilots. Shoutmon is Ryoma (and Getter-1 is red and has a V crest!), Dorulumon is Hayato (loners and former criminals, and Getter-2 has drills!), and Ballistamon is Musashi (both are the The Big Guy of both teams).
The way X3 actually combines, meanwhile, is almost identical to the SRX from Super Robot Wars: the leader rides inside the core of the combined form, with his personal weapon splitting into a helmet and sword hilt; a bulky blue robot forms the torso and arms; the third member splits into three parts which become a pelvis and legs.
The DigiMemories are also this, as they call upon the power of notable Digimon from the previous series and card game.
Shoutmon's ROCK DAMASHI!note Rock Soul is essentially Hydro Blazer.
Monitamon's head and color scheme are modeled after the Zaku II.
Victorize Boomerang is essentially a homage to Breast Boomerang. Later version can also unleash a devastating Chest Blaster. Which is a recycled idea from Ulforce Veedramon
AncientVolcanomon is... large, rotund, and has a tendency to have temper tantrums unless quelled, and gets killed via exploding. It's Mr. Heart-mon!
Shoutmon X3/X4 is already a massive shout out to one of his predecessors, Omnimon. In the Lake Zone arc, this gets even more prominent with Shoutmon X4 Knight, in which he gains a cape, a sigil-emblazoned shield, and a new version the Star Sword that heavily resembles Omnimon's own massive blade. Now he just needs a cannon...
Tactimon's design is pretty much resembles a Kamen Rider turned into a Digimon (huge eye lens, armor, mouthpiece, you name it!).
Shoutmon X5B has an attack called Victorize 5B. Outside of the Chest Blaster reference to Mazinger Z, Shoutmon X5B stretches his arms in a V-like symbol too, causing a V-shaped energy to form, similar to Voltes V.
People will say BEAT SLASH! is a Tengen Toppa Gurren Lagann reference, but consider this: he fires two fireballs (HARD ROCK DAMASHI!) to hold the foe, before performing a piercing kick that leaves a circular hole on the foe's body. Sounds more like Daitarn Crash!
Another similar attack from Daitarn 3 is Shoutmon DX's VICTORIZE BANKING! His V crest on his head glows red which then fires multiple V-shaped energy at the enemy, much like Sun Attack Midrange in the Super Robot Wars.
The Seven Death Generals in the second season is a throwback to the Seven Generals in Great Mazinger, complete with similar themes!
Most of the Digimemories are past heroes from previous series. This Shout-Out is taken Up to 11 when Omegamon reveals that the Digimemories are actually the sealed forms of a group of heroic Digimon that protected the Digital World in the past.
Bagramon seems to have have taken some cues from Lordgenome, as both are mostly portrayed as sitting on their thrones and ordering their generals around most of the time, despite being extremely powerful on their own. Bagramon is a Fallen Angel while Lordgenome was a Fallen Hero, and they both have incredibly badass beards. Of course, this would in turn also make Bagramon a bit of a shoutout to Master Asia as well, whom Lordgenome was partially inspired by.
Yuu thinking the Digital World was a game, the later realization of his actions, and the death of his partner Damemon sounds pretty familiar.
Essentially, thanks to reveals involving season 3, this whole series will be a Shout-Out. Time traveling back to previous times and worlds in the series. All the continuity charts fans have made so far? Fucked. Every destined child from all other seasons will be appearing at some point, WITH their Digimon.
A few from the manga: JagerDorulumon is very reminiscent of MirageGaogamon, and Shoutmon EX6 has an attack called SoulCalibur.
First, look at the title. Now, the show is full of Seiyuu jokes, Shout outs to different shows, and the previous shows before Xros Wars. The show as a whole has an appearance of Older digimon from previous series, and Newer digimon. The Digimon fights in a War against each other until one Big Bad evil faction shows up and everyone join forces and fight against said faction. Sounds rather familliar huh ?
Gargoylemon is a strict upholder of the rules in Heaven/Sky Zone (populated by angel and fairy typed Digimon), and in the dub has a stock Arnold Schwarzenegger impression — a surprising shoutout to Jorgen von Strangle.
Episode 21 has Pinocchiomon (who is a good guy here) giving the Taiki a MetalGarurumon DigiMemory. Now, look back at Digimon Adventure...
Episode 20 is a bit of this along with Mythology Gag, given that the episode is about Pinocchiomon learning to trust others and believe in his friends. Once again, look back at Digimon Adventure (heck, look at his quote on the characters page).
Another in Episode 21 - MetalGreymon's armored hand begins to glow in gold, which he then used to smash SkullGreymon's face.
Episode 23 has Karatenmon, who even attempted to do a certain laugh. His voice actor is the same one voicing King Kai.
Episode 24, the episode where Nene obtains the purified Xros Loader, has the Monitamon rookies do a certain pose (and color!) before becoming into Hi-Vision Monitamon.
Episode 26 debuts Damemon's true form, Tsuwamon. A golden ninja who is basically Shurikenger if he was a Digimon. Heavy on the random Engrish too
Again in Episode 26, Cutemon says "There's only one truth!", a reference to Detective Conan. Hilariously enough, Taiki's voice actress does Conan's voice. Also, Taiki's last name is 工藤 (Kudoū) - the surname of Conan's real name, which may or may not be deliberate.
Also in episode 26, when Beelzebumon Xrosses with Revolmon, it gives him a red scarf wrapped around his arm like his Expy counterpart's red bandanna. (Unfortunately, the artists forgot to draw it every frame so it sometimes disappeared.)
Episode 27 has the gang go to the Sweet Zone and have to participate in a sweets making battle before they can meet Matadormon. Before the battle starts the ref bits into a bell pepper. If you don't get it, watch more Iron Chef (not the American one).
Episode 30 has Omegamon saying that Shoutmon's digivolution into OmegaShoutmon was made possible by the courage and friendship of Akari and Zenjiro. The original Omegamon was a Jogress of WarGreymon and MetalGarurumon, who were partnered to the original Digidestined of Courage Tai/Taichi and Digidestined of Friendship Matt/Yamato.
Moreover, OmegaShoutmon bears more than a passing resemblance to Magnamon, whose partner Davis/Daisuke held the Digimetals of both Courage and Friendship.
And it even has that aurora found in that episode in Adventure where Tai went back to the real world.
Many people, after seeing episode 48, have declared that Lilithmon turns into the Devil Gundam.
Beelzebumon's "Death the Cannon" attacks seem very much to be referential to Death the Kid from Soul Eater.
Both this Beelzebumon and the one from Digimon Tamersdied or were fatally wounded in episode 48 of their respective seasons.
In episode 49, Apollomon and Shoutmon X7 engage in a Beam-O-War that is very, very reminiscent of Dragon Ball Z, especially the ending of the second Broly movie with Apollomon using a gigantic energy sphere and X7 trying to block it with his energy beam.
Prison Land is a bleak desert with withered trees where torn-off souls are sent. It's Hueco Mundo!
The idea of every being in the world parallel to our own lending their strength to the hero, resulting in godly power and a golden upgrade is rather familiar to those who read the final battle with the Big Bad of Zatch Bell!.
Not only that, but Omegamon (who appears as a Digi Memory) was originally formed as described above in the Digimon Adventure movie in case you don't remember, all of the good feelings towards Greymon and Garurumon get used to power up Omegamon/Omnimon, while all of their e-mails are used to stop their enemy.
The dub of course had to get in on the fun sooner or later — in episode 4, Jeremy lets out a "Yoinks, and away!" before jumping into the portal to the next zone.
Also in the dub, Mikey describes Shoutmon's logo design in episode 3 or whereabouts as an "angry parakeet". He's not wrong.