Technosqueek
From Sonic Retro
Technosqueek, called Chu-chu (チューチュー) in the Japanese Manual, is a rodent-like badnik from Sonic & Knuckles found in Flying Battery Zone designed to look like a computer mouse. They are found scuttering in ceilings, walls and floors. Jump on them to destroy them. "Chu-chu" is Japanese for squeak.
Since Sonic 3 and Sonic & Knuckles were one single game split in half, the Technosqueek was listed by accident in the Sonic 3 manual's badnik section.