Mousers are robots created by Baxter Stockman with the purpose of burrowing underground to steal valuable items for their master. Their name is an acronym for "Mobile Offensive Underground Search Excavation and Retrieval Sentries", indicating that dealing with mice and rats was not their original purpose. Ironically, their vocals sound like cat meows.
- The Mouser has for his head, a bicycle helmet used in the City theme.
- It has also Shredder's claws as feet.
- M.O.U.S.E.R.S. stands for Mobile Offensive Underground Search Excavation and Retrieval Sentries.