Chet is a mouse that appears on the show as Ruff's assistant. He has first appeared in Season 3 and has been there ever since.
He is a brown mouse with no eyes. Like Blossom, he's a mute character with the occasional cartoon sound effect. He somewhat takes things literally like when Ruff says "Burn It" meaning to put the wet kibble in the trash, he instead puts a building on fire. Or when Ruff Blossom & Chet try to do a "Bluejay". He gets paint and puts it over Jay's face, the winner of Season 3. He also does things that are impossible like building a jet engine made that runs on milkshakes. At first, Ruff didn't like him. But he now starts to become more of a friend to him.
Chet lives within a small mouse hole of the left side of the Fetch 3000. He seems to have many things Ruff doesn't have or can't afford, like a jacuzzi. Chet is mostly a troublemaker, but sometimes Chet does what Ruff tells him to do, which is why Chet can stay.==