Originally introduced in the 1937 short Porky's Romance, Petunia Pig looks much like her significant other, except that she wears a dress and has braided black hair.

George P. Dog (better known as Barnyard Dawg) is an adult anthropomorphic basset hound. He is usually seen sleeping in his kennel at a cartoon's beginning, with Foghorn provoking him by slapping his hindquarters with a wooden fencepost, setting the stage for Dawg to seek vengeance.

Gossamer was first introduced in the 1946 short "Hair-Raising Hare", in which Bugs Bunny was lured to the lair of Dr. Lorre, a mad scientist who wants to use the rabbit for his experiments. The then-unnamed monster served as the scientist's henchman. A toddler version of Gossamer appeared in the Baby Looney Tunes episode "Stop and Smell Up the Flowers" where he frightened the other baby loonies.

Bosko, a sort of human version of Mickey Mouse with a bowler hat and falsetto voice, was the star of 39 Looney Tunes shorts released by Warner Bros during the 1920s and 1930s. In 1933, when Bosko's creators Hugh Harman and Rudolf Ising left Warner Bros over budget disputes, they had carefully kept all rights to the Bosko character and took him with them.

Originally a one-shot character, Michigan J. Frog's only appearance during the original run of the Merrie Melodies series was as the star of "One Froggy Evening" (1955), in which Michigan's vaudeville talent is discovered by a hapless man who has visions of profiting from it, but catches on too late that the frog will perform for him and him alone.

Speedy Gonzales is portrayed as "The Fastest Mouse in all Mexico." His cousin, Slowpoke Rodriguez, is the "slowest Mouse in all Mexico."

In almost all her appearances, Granny is depicted as the owner of Tweety (and more often than not, Sylvester the Cat and Hector the Dog as well).

In The Scarlet Pumpernickel (1950), Daffy has a middle name, Dumas as the writer of a swashbuckling script, a nod to Alexandre Dumas. In the Baby Looney Tunes episode "The Tattletale", Granny addresses Daffy as "Daffy Horatio Tiberius Duck". And in The Looney Tunes Show (2011), the middle names "Armando" and "Sheldon" are used.

Haredevil Hare stars Bugs Bunny as an unwilling astronaut who saves the Earth from the Mars to Moon Expeditionary Force, which consits of Marvin the Martian and his Martian dog, K-9.

On numerous occasions, Marvin has tried to destroy the Earth with his "Illudium Q-36 Explosive Space Modulator". He always over-pronounces the name of the device, which resembles a stick of dynamite, in order to avoid any possibility of confusing it with some other, more primitive type of explosive technology.