Jeweler's Eye Loupe: In the short Goo-Goo Goliath, the drunk Delivery Stork switches of the families of a human baby and a giant baby (because the giant one was too heavy to fly to the top of the beanstalk). At the end, we see the adult giant taking care of the human baby, using an eye loupe to change his diapers.
Joker Immunity: Some of the star characters meet untimely demises at the conclusion of their cartoons (Daffy in "Daffy Duck and the Dinosaur" and "Show Biz Bugs," Yosemite Sam in "Dumb Patrol," Sylvester in "Tweety's Circus") and are seen as good as new in their next six-minute installment thanks to Rule of Funny.
Judicial Wig: In "Bugs Bonnets", Bugs and Elmer keep changing roles depending on the hats that end up landing on their heads. At one point, Bugs as a gangster tries to bribe Elmer as a cop. Elmer tries to give the bribe back, but at that point a judge wig lands on Bugs, who then sentences him for corruption.
Kangaroo Pouch Ride: In "Daffy Duck Slept Here", Daffy claims that he has an invisible kangaroo named Hymie. Porky doesn't buy it, so Daffy climbs up on an invisible pouch and his disembodied floating head is seen bouncing all over the room. Even so, Porky still doesn't buy it.
Daffy Duck antagonists Nasty Canasta and Rocky the Gangster were sinister imposing thugs (and even got away with their actions). Naturally when they ended up in the Bugs Bunny series afterwards, they took a serious downgrade in menace.
Daffy himself acted like this is a few of his pairing with Speedy, notably in "Assault & Peppered" and "Well Worn Daffy".
At least four Jekyll-and-Hyde-type examples:
The lawyer from "The Case Of The Stuttering Pig".
Mr. Hyde from "Hyde and Hare".
The transformed Sylvester from "Dr. Jerkyl's Hide".
In From hare to Heir, Yosemite Sam hides in a tiny suit of armor to attack Bugs with an axe. However, he misses and proceeds to take a tumble down a long flight of stairs, cussing all the while.
Gossamer tried this once with a suit of armor, but his hair leaked out of the edges of the parts of the suit.
Koosh Bomb: Where it became famous. Especially the Roadrunner cartoons.
Lame Pun Reaction: Meta: In the "music only" audio track for "The High and the Flighty" Note (a parody of "The High and the Mighty", a WB disaster film from 1954), when the conductor announced the name of the cartoon, the musicians chuckled derisively and groaned.
Large Ham: Every character in the main cast (and maybe a few from the minor cast)
Last Note Nightmare: Uncharacteristically for Milt Franklyn, "Mother Was a Rooster" ends with a dissonant, loud chord.
Later Installment Weirdness: The original studio briefly shut down in 1963 and Depatie Freleng Enterprises (opened the same year) took over until 1967, when Warner Bros. Animation reopened again, but there were some downright bizarre changes in direction for the franchise during its final six year period, to where even the original Harman-Ising era cartoons have more in common with the more iconic Looney Tunes than these later cartoons:
First, and most notably, is that there were no more new Bugs Bunny cartoons made.
Second, Daffy Duck, previously a comedic goofball or hopeless loser, became a straight-up antagonist to Speedy Gonzales, who became the recurring stars of these later cartoons.
Third, a new crop of characters, including Cool Cat, Bunny and Claude and Merlin the Magic Mouse, were introduced in 1967. The tone and humor of their cartoons has little in common with the other Looney Tunes series. The last ten shorts of the franchise would star these newcomers instead of any of the original characters.
After 1964, no new oneshot cartoons were made, with the exceptions of "Norman Normal" (which was billed as a Cartoon Special instead of a Looney Tunes or Merrie Melodies short), "Flying Circus", "Chimp & Zee", and "Rabbit Stew and Rabbits Too".
Fourth, the art direction and animation discarded full animation and the studios original slick house style in favor of very Limited Animation and heavily stylized designs in vogue with the TV cartoons of the day. Character shorts (i.e. Bunny and Claude) and one-shot shorts alike (i.e. "Norman Normal", "Bartholowmew Vs. the Wheel") look completely out of place in the series as a whole.
Fifth, the directors strong individual styles (the few left over anyway, which included Friz Freleng and Robert McKimson) practically vanished into ether, with ultra formulaic meat & potatoes cartoons popping up in their steed.
Sixth, the traditional "concentric circles" opening and closing logos were dropped in favor of the more modern "Abstract WB" logo sequences accompanied by a klunky, atonal version of "The Merry-Go-Round Broke Down," arranged by Bill Lava, originally devised by Chuck Jones for use on his "Now Hear This" in 1963, and then went on to be used on two more similarly-stylized one-shots before being used on all new cartoons after Depatie-Freleng took over. The logos were subsequently updated when Warner Bros. merged with Seven Arts in 1967 to included their "W7" corporate logo. They no longer even used the phrase That's All, Folks! during the closing titles.
Sylvester did this in "Muzzle Tough" (1954), posing as a female dog (it's so convincing it fools a dog catcher!)
He also did so in "Fowl Weather" (1953) when disguised as a goat (which Tweety managed to identify the true identity of anyway.)
Daffy Duck also did this at the end of "What Makes Daffy Duck" (1948) wearing a rubber dog mask to make his ranger-dog disguise flawless.
Ralph Wolf also features this in "Don't Give Up the Sheep" (1952) when perfectly disguised as another sheepdog.
A few cartoons have also revolved around this trope for more than half of the short, including "I Got Plenty of Mutton" (1944, a wolf disguising himself full-body as a sexy female sheep to lure a ram away from his protected herd, which works all too well, and "Paying the Piper" (1949, the Supreme Cat wears a full rat suit and mask to provoke Pied Piper Porky with).
Lazy Artist: It's extremely rare, but it's quite noticeable when it happens. Two occur in 1943's "Porky Pig's Feat": As Daffy issues a challenge to the hotel manager, a cel of Daffy is photographed painted side up in a frame (The redrawn version even renders that errant cel drawing!). At the end when Porky and Daffy discover Bugs Bunny in the adjacent room, Daffy's left arm is shown unpainted.
Lampshaded in "Invasion Of The Bunny Snatchers" (1992). Pod carrots from space replace Daffy, Yosemite Sam and Elmer with poorly drawn and animated duplicates.
Also seen in "Odor of the Day" (1948), when Pepe Le Pew (disguised as a doctor) carries a flattened dog on a stick he walks with a limited animation walk cycle (the kind Hanna-Barbera and Rocky and Bullwinkle usually did.)
As yon weary traveler enters his castle on his steed in Robin Hood Daffy, the edge of the cels on which he's drawn can be seen for about a second.
Bob Clampett's "Tin Pan Alley Cats" (1943) pads out some two minutes with reused animation and backgrounds from Porky In Wackyland. The reused art is recrafted in color.
Legacy Character: The cat chased in Pepe Le Pew shorts varied from short to short, in both appearance and name, though these days is referred to by the consistent moniker Penelope Pussycat (which she was named in 1954's "The Cat's Bah.")
Some sources give the name Brownie Mouse to various rodents used in Sylvester cartoons.
Leitmotif: The opening jingle of "Stage Door Cartoon" was recycled in numerous late 40s/early 50s shorts as the theme for Bugs Bunny (and was later used as the tune for "What's Up Doc?").
Carl Stalling had a tendency to associate tunes with specific characters. Foghorn Leghorn sings or hums "The Camptown Races" in numerous shorts.
"I Cover the Waterfront" was often used during establishing shots of docks and harbors.
"Baby Face", "Oh, You Beautiful Doll", "It Had To Be You", "The Lady in Red", and "You Must Have Been a Beautiful Baby" were often used when a beautiful woman was on-screen.
"A Cup of Coffee, a Sandwich, and You" or "Shortnin' Bread" often played whenever a character was eating or preparing food.
"Trade Winds" often accompanied tropical settings, while "Winter" was used in snowy settings.
"Over the Waves" and "She Was an Acrobat's Daughter" were frequently used in acrobat/swinging sequences.
"Rock-a-Bye Baby" was used for baby-centric scenes, or characters trying to get another character to sleep.
"How Dry I Am" and "Little Brown Jug" were reserved for drunk characters.
"I'm Looking Over a Four Leaf Clover" and "In My Merry Oldsmobile" were used in automobile/highway sequences.
"Blues in the Night" (aka "My mama done told me...") was often used whenever a character experienced bad luck or was down in the dumps.
"Frat" and "Freddie the Freshman" were almost always used in sports scenes.
"Me-ow" was a recurring cat-based theme.
"Der Erlkönig" was often used for Yosemite Sam, but was also heard in non-Sam shorts, usually accompanying evil characters.
"I've Been Working on the Railroad" was used for train and/or train tracks gags.
"We're in the Money" was used countless times when a character either received riches or was dreaming of it.
"Hooray For Hollywood" and/or "You Ought to Be in Pictures" played whenever Hollywood was involved.
"Pretty Baby" often played when babies were on-screen.
"You're in the Army Now", "We Did it Before (and We Can Do It Again)", and "Columbia, Gem of the Ocean" were used for war cartoons/gags.
"You're a Horse's Ass" was used whenever a character realized they fell for a prank or were insulted. Appropriately, it was also used as the main theme for Private Snafu.
"William Tell Overture" (Finale Movement) was usually used for horse-riding scenes. The Storm Movement was used, appropriately, for storm sequences. "Ranz des Vaches" was used for sunrise sequences.
"Sweet Dreams, Sweetheart", "Too Ra Loo Ra Loo Ral" and "Brahms's Lullaby" were used for sleeping gags/scenes. Occasionally, "By the Light of the Silvery Moon" was used if said scenes also involved the moon.
When Bill Lava took over as composer, he created an opening fanfare for Bugs Bunny cartoons. This fanfare was used for four cartoons, "False Hare", "Hare-Breadth Hurry", "The Iceman Ducketh", and "Mad as a Mars Hare".
Bill Lava also had a recurring theme for Speedy Gonzales during the 1964-1968 era. A variant of it was used as the title music for "The Music Mice-Tro."
Let's Get Dangerous!: Any time Bugs Bunny says, "Of course you realize... This Means War!!", you can be certain that whoever provoked him like this will soon be entering a world of hurt.
Limited Animation: Some of the best uses of this format in cartoon history. Most cartoons in the '30s and '40s utilized full animation just like Disney and other contemporaries. However, Chuck Jones experimented with limited animation in The Dover Boys, liberally using quick smears and held poses. But limited animation (that is, less actual character movement) was never widespread until the mid '50s, when budgets got slimmer. Nevertheless, the various units worked around the limitations quite well, even if the animation wasn't as full as the previous two decades.
Played straight with the "Larriva Eleven" (that is, eleven Road Runner shorts directed by Rudy Larriva instead of Chuck Jones) and three Daffy/Speedy shorts from 1967, all outsourced to Format Films.
Limited Special Collector's Ultimate Edition: From 2003 to 2008, Warner Bros. released the Looney Tunes Golden Collection series, spread across six volumes and covering over 400 classic cartoons, hours upon hours upon hours worth of commentaries, documentaries, interviews and historical bonus content in general. However, for the kiddies, a Vanilla Edition series of these DVDs were released called Looney Tunes Spotlight Collection, which were essentially bare bone collections featuring the more well known, family friendly Looney Tunes shorts. The new single-disc Super Stars DVDs follow the Vanilla Edition practice, but the Platinum Edition line is a continuation of the Golden Collection-style releases.
Lighter and Softer: Contemporary revivals of the characters (most egregiously the 90's and 2000s ones, where Warner Bros. were really trying hard to cash in on the franchise) tended to downplay or outright eschew the violence and politically incorrect humor of the original cartoons, and portray the Tunes as friends rather than constant comedic adversaries. This and the outdated context of the cartoons has unwittingly led to the misconception that Looney Tunes, which were originally made for general (learning more towards adult) audiences, were intended as childrens cartoons. Invasion Of The Bunny Snatchers was specifically made to satirize just how watered down the Looney Tunes had become by then.
Loser Gets the Girl: In "Muscle Tussle", Daffy loses his girlfriend to a big, white muscular duck at the beach. A series of blundering attempts to impress her eventually injure his rival and thus win her back.
Lost in Imitation: Contrary to what it may seen, Porky Pig never did his signature "That's all, folks!" sign-off on the traditional concentric circles background in the classic cartoons. This was mainly done in parodies, such as in Kangaroo Jack or The Muppet Show. In the classic Looney Tunes shorts, Porky said it while breaking out of a drum. However, some recent Looney Tunes productions, such as the 2003-2004 shorts, have Porky give his sign-off in the concentric circles.
Loveable Rogue: Charlie Dog (the dog who always harasses someone — usually Porky Pig — to be his master). Daffy sometimes played this role as well (especially under Robert McKimson's direction).