King Size Canary is a landmark 1947 Tex Avery cartoon made during his MGM tenure. This oneshot short is centered around a hungry cat who, in an attempt to get more meat out of a pea size canary snack ("Well... I'm sick."), pours a bottle of Jumbo Gro Plant Growth formula on him - only to make him grow to gargantuan proportions. The cat drinks some himself to keep up, and soon a mouse gets involved as well. The tables keep turning and turning as one of the other keeps drinking more of the formula as their battle continues.
An unnamed alley cat searches for food in some garbage cans late at night. Unable to find anything worth his while (the bones he finds are stolen by other alley cats before he can take a bite) he spots a refrigerator inside a house and heads for it. He sneaks onto the property only to wake a sleeping bulldog. The bulldog chases the cat up to the side of the house. The cat quickly pulls out somesleeping pills, putting the dog into a deep sleep.
Once inside the cat searches for food in the kitchen, but comes up empty. His luck finally changes when he finds a can of cat food. He quickly opens the can and out of the can pops a mouse who is plopped down onto a dinner plate. The cat is about to dig in with a fork but the mouse puts a quick stop to that. He says that the cat can't eat him because he has already seen the cartoon they are in and that he winds up saving the cat's life later. The feline understands but wants some food as he is starving. The mouse points into the other room and tells him that there is a huge, fat, tasty canary in there. The cat charges out into the other room and stuffs the unseen canary into a sack heading back to the kitchen.
The bird is emptied from the sack, to be revealed as scrawny and little. The bird tells the cat, "Well, I've been sick..." Disgusted with the tiny creature at first but still desperate, the cat gets a (literal) brainstorm when he sees a bottle of Jumbo-Gro plant growth formula on the shelf. Quickly he pours some of the formula into the bird and sure enough, the canary grows rapidly in size. But before the cat can take a bite, the bird is already over 10 feet tall. The canary takes advantage of his new height and beats up on the cat. The cat turns the tables on the bird and drinks the Jumbo-Gro formula himself, doubling in size until he is much bigger than the bird. He tosses the potion out of the window only for it to land in the bulldog's mouth. While the now giant-sized cat chases the slightly smaller canary through the side of the house, the bulldog guzzles down the formula. After a quick run around the block, the cat and canary wind up back outside of the house, where a now gigantic bulldog appears before them. The cat runs away in fear as the bulldog tosses the bottle of plant growth food down the chimney, where it rolls out of the fireplace and straight to the mouse inside the house. The dog leaps over the house and chases the cat into the city.
The mouse in the house takes a few sips of plant food, instantly ballooning to gigantic size. The dog chases the cat to the city, only for the now gargantuan mouse to show up and scare the bulldog away with a simple "Boo!". The mouse who is as tall as a 20 story building and just as fat, reminds the cat that he told him he would save his life. The cat thanks him as the mouse hands him the bottle back and waddles off. The cat, rubs his enormous belly realizing he still is hungry, sees the huge mouse stomping off and gets another idea. He suddenly drinks more of the formula and grows even bigger and fatter than the mouse. The cat who is by now 100 stories tall, chases the giant but smaller mouse through the city and across the country, passing the Grand Canyon, Hoover Dam and the mountains.
The giant mouse hides in a railroad tunnel, losing the cat for a moment. The mouse drinks the potion when the cat isn't paying attention and becomes even bigger than the already huge cat. The mouse starts to beat up on the cat only for the cat to take the potion back and drink it, becoming bigger than the mouse. The mouse takes it back and drinks more to become bigger still. They continue getting bigger and bigger, fatter and fatter until they suddenly both come to a stop at the same exact size. They shake the now empty bottle of Jumbo-Gro and tell the audience at home that they have to end the cartoon, as they've run out of the formula. They wave goodbye to the audience before the camera pulls back, revealing that they have outgrown the Earth themselves and are standing atop the globe.