Frog

Frogs are real-world amphibians that have appeared in various roles throughout the Mario franchise and other related franchises. While the first appearance of a frog in a Mario game was Super Mario Bros. 2, which marked the debut of Wart, non-sapient generic frogs started appearing in Super Mario World 2: Yoshi's Island as minor interactive entities.

Super Mario World 2: Yoshi's Island / Yoshi's Island: Super Mario Advance 3
In Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3, green and brown frogs appear as ambient species. They mainly inhabit wet climates, such as World 3. They are seen hopping continuously in one direction, switching directions whenever Yoshi approaches them. They can disappear by jumping into a body of water. However, they will respawn in their initial spot after Yoshi leaves and returns in their area. Additionally, Frog Pirates are a larger variety of frogs that grab Baby Mario using their tongues if a Yoshi approaches. The mid-boss of this world is known as Prince Froggy. Unlike the other bosses, this one does not get altered by Kamek's magic.

Diddy Kong Racing / Diddy Kong Racing DS
In Diddy Kong Racing and its remake, several frogs live in the pond in the hub. One of these frogs, who has a tell-tale red crest upon its head, is actually Drumstick, who has been put into frog form by Wizpig. He can be freed if the player runs over him in a car.

Luigi's Mansion: Dark Moon
Frogs appear again in Luigi's Mansion: Dark Moon. In this game, they are pigmented with warm colors, with most of their body being red. They croak when discovered and act as ambiance creatures. They do not actively try to injure Luigi, but can drain five heart points from his health meter if they run into him. They can be defeated with the Strobulb, dropping a Coin once they disappear.

The Frogs are mainly found in the Haunted Towers. They also show up in the final King Boo battle, with special giant versions of the regular frogs appearing as well, which may spawn from spiked balls after King Boo slams the ground. These giant frogs, however, do not grant any treasure upon getting flashed with the Strobulb.

The game also features a more precious variant of frogs called Gold Frogs, which reward Luigi multiple Gold Bars if he uses the Strobulb on them. Gold Frogs can be primarily found on the East Balcony of the Treacherous Mansion.

Super Mario Odyssey
Small, harmless frogs appear in Super Mario Odyssey, where they can be found in Bonneton, Honeylune Ridge, and the Darker Side. They can be controlled by Mario and Cappy and are also the first capture found in Super Mario Odyssey. When captured, frogs give Mario the ability to jump higher and shaking the Joy-Con causes Mario to perform a High Jump, allowing him to reach even higher placed platforms. Mario can also defeat Mini Goombas by simply running into them while capturing a frog, since they hop along the ground as they move instead of walking. Like most enemies, they disappear after a while when Mario de-captures them. Sometimes before being captured, they wear small top hats. A plush frog is also a souvenir for the Cap Kingdom. According to the Moon Kingdom brochure, the frogs there were brought by the Moon's first pioneers; seeing a "Moon Frog" is said to be a good omen. Jumping on a frog rewards Mario with one coin, but this does not affect them.

Yoshi's Crafted World
Origami frogs appear in Yoshi's Crafted World in the level Hoppin' Higher. In this game, they constantly jump in one spot. If Yoshi ground pounds them, they hop higher.

Trivia

 * In an E3 demo of Paper Mario: The Thousand-Year Door, Hooktail had a strong dislike toward frogs, but this was changed and Hooktail was given the hatred of crickets. However, she is still afraid of frogs in the translated versions of the game other than English.