Bananas

Role
Bananas (Also known as TS-02) was the second ever test subject to be a part of one of the Kitatcho Laboratories testing tracks. Being a monkey (although the exact type of monkey is never mentioned), Bananas was part of an experiment to see if animals shared the same cognitive abilities that humans did when it came to testing.

Not much is known about Bananas, however from the information that we're given it's safe to say Bananas was an above-average monkey who solved chambers much faster than the player (TS-03).

Death
Bananas sadly passed away when making it to Chamber 12 of Test Track 02. While many scientists believed the introduction of lava and fire resistance plates would cause his demise, it actually turned out to be the fault of him dropping one of his own banana peels on the floor and slipping on it, thus causing him to fall and smash his head on the chamber floor. This unfortunately caused Bananas to bleed out to death. A small dried up blood stain can be seen in Chamber 12 when the player ventures through Test Track 02, signifying where Bananas took his last breath.

Who gave him the banana in the first place? Perhaps we'll never know.

Memorial
In The Kitatcho Laboratories: Chapter 2, there's a small memorial outside of Ki-Tacos between chambers 06 and 07. This memorial is dedicated to Bananas, who confirmed he lived from 1997 - 2007.