From Sonic Retro
Mono Beetle, モノビートル, is a GUN robot that appears in most of the stages of Sonic Adventure 2 and part of the Beetle series. It's the most basic of the series, and is used as a base from where all the other models are designed and modified from. It has no attacks and stands still only to excitedly move up and down slightly when it spots a character. Sometimes, it might be invisible and suddenly appear when a character comes near their position. It awards 100 points when destroyed.
|Sonic||City Escape, Green Forest, Crazy Gadget|
|Tails||Prison Lane, Eternal Engine|
|Shadow||Radical Highway, White Jungle, Sky Rail|
|Eggman||Iron Gate, Sand Ocean, Lost Colony, Cosmic Wall|
|Sonic Adventure 2|