He's a dolphin that's a criminal loan shark who does very shady and secret jobs for people in exchange for money. The Loan Dolphin has a black leather jacket and sometimes smokes cigarettes. As well he tends to have his operations in the shadiest places, but are usually in the same building. (copy and pasted from the SML wiki)

Mooshroom is a Gamer and an Engineer, he actually created the rocket with the massive catapult on it, The Rocket takes place in MM Movie: "The Asteroid Problem!" which is launched onto the episodes asteroid "2019-BM2009", he also has an extraordinary love for burritos.