Monkey Yellow (ウッキーイエロー Ukī Ierō?) is the extremely fat, as well as disturbing, member of the Freaky Monkey 5. He first appeared in Ape Escape 2 with a sumo wrestler motif. When he eats more Vita-Z bananas than he's supposed to, he can grow to sizes equal to that of a skyscraper's. When he did, Jimmy had to fight him by knocking his rotten teeth out with the stun club. In P&P, he is referred through a fan letter, saying that he needs false teeth. He reappears in AE3 again as a wrestler, but this time fighting ninja-style, reprising his role as a Freaky Monkey Five member. In the Ape Escape anime, he is dressed as a chef and carries a giant fork with him. (This could be a reference to Final Fantasy IX's Quina Quen, a genderless creature much like Yellow Monkey a male who would love to be female).
Yellow Monkey is very strong, though nowhere near as strong as Red Monkey, and despite his size and build he is actually very swift. Yellow Monkey is one of the most interesting members of the FMF, as he is the only member whose body color is the same as in his name (excluding Pink and White) and his physical appearance has been changed so much that he's barely even noticeable as a monkey. This may be in part due to Vita-Z bananas, which seem to have increased his size greatly. This is revealed when you defeat his giant form in the second game, and he is shrunk to the point where he's almost smaller than Pipotchi. Though it's revealed that Yellow Monkey is a male, it should be noted that he has an extremely feminine voice in his first appearance. In Ape Escape Academy, his name is Ukki Yellow. In rank of strength, Yellow Monkey lies within the range of third strongest. His different styles of fighting help keep a battle going, but he doesn't have as many attacks as Pink or Red.
In AE2, he is portrayed as a sumo wrestler, who's battlefield is a wrestling ring with spikes protruding from the area around it. His attacks involve charging at the player (opening up the chance to knock him into the spikes with the Stun Club) and stomping the ground, causing objects to fall from the sky and crush the player. He swears revenge and runs away, later returning as a giant, which the player must defeat.
In AE3, he is portrayed as a sumo wrestler again, but with the abilities and agility of a ninja. His signature move is entitled Ninja Attack, in which he jumps to an area too high to reach even with the Sky Flyer and tosses throwing stars, some attached to ropes in which Kei or Yumi can climb as the Miracle Ninja, to the ground.