On alternate occasions, Gabriel Marin pretends to be excessively neurotic, excessively hedonistic, excessively wounded, or excessively vulnerable. But he’s always excessive. Marin has the kind of easily mutable features that make emotions legible on his face. In last year’s fabulous comedy Jack Goes Boating (which closed the 2008-2009 season at Aurora Theatre), he played one-half of an eccentric husband-wife duo. As the husband, Clyde, Marin was fussy and temperamental, with a real short fuse. He worked for a limo service by day and took a side gig teaching tai chi swim lessons — for which he acted more like an army drill sergeant. CenterRep’s production of A Number had him playing sons cloned from the same petri dish. The role required Marin to straddle that fine line between nature and nurture, showing how three distinct personalities could inhabit the same body. Playing opposite veteran actor James Carpenter, Marin shifted characters with ease.