Whale

A Whale is a large marine mammal mostly found on Earth, but first appeared in the Mario game Super Mario Bros. 2.

Super Mario Bros. 2
Whales appeared in level 4-2 of Super Mario Bros. 2. Players can hop on their backs and gain elevation by standing on their blow holes as water sprays out. The water will hurt the player if they touch it from either side.

The Super Mario Bros. Super Show!
A Whale briefly appeared towards the end of The Super Mario Bros. Super Show! episode "Mario of the Deep". Here, the Whale was rode on by King Neptune, who was using it to body slam his temple, which Barra-Koopa had taken over, along with the rest of Aqua Land. After slamming into the wall several times, the Whale caused a piece of it to shatter away, which Mario, Luigi, Princess Toadstool and Toad were able to pass through. This Whale appeared to be a Blue Whale rather than the variety of Whale from Super Mario Bros. 2.

Paper Mario
An individual Whale appeared as a character in Paper Mario, where he aided Mario and his allies by getting them across the sea to Lavalava Island.

WarioWare, Inc.: Mega Microgame$
The whales from Super Mario Bros. 2 also appear in WarioWare, Inc.: Mega Microgame$ in one microgame.

Donkey Kong Jungle Beat
In Donkey Kong Jungle Beat, a Killer Whale named Orco appeared as an ally to Donkey Kong.

Wario: Master of Disguise
In Wario: Master of Disguise, a species of cyborg whale called Cyborca appeared as enemies in the game.

Super Mario Land 2: 6 Golden Coins
In Super Mario Land 2, Mario has to go inside a Whale and travel to the Whale's end in order to defeat the boss, an octopus.

Nintendo Monopoly
A whale makes a cameo in Nintendo Monopoly.