At the end of the episode "The Schizoid Man", it is implied that Data wrestled a Klingon targ:
RIKER: Does wrestling with a Klingon targ ring a bell?
PICARD: Mr. Crusher, take us out of orbit.
WESLEY: Aye, sir.
DATA: Did I win?
Why would the Enterprise have a targ aboard? Is it someone's pet? (Worf had a pet targ as a child, but he does not appear with a real one as an adult.) Is it food? Is it being carried as cargo?