Joaquin is Numbuh 2's most often used hamster in experiments in Sector V.
In Operation: G.H.O.S.T., he leads the other hamsters to beat their evil ghostly counterparts using sodas.
In Operation: K.I.S.S., Joaquin appears, transforming Numbuh 2 into a teenager, who, in turn, fell in love with Numbuh 5's older sister, Cree. He later attempted to try to use the ray on himself, only to cause the power in the treehouse to fail, leading to the rest of the events that occurred in that episode.
He makes another prominent appearance in Operation: F.O.O.D.F.I.T.E., as he used the same ray in response to Sector V's call for help against Grandma Stuffum, growing to an enormous size with a very muscular physique in order to fight Slamwich. He defeats the creature by devouring it, thus saving Sector V.
In Operation: Z.E.R.O., he is noted by Numbuh 1 as one of the citi-zombified hamsters.