Marcel was Ross' pet Capuchin monkey on Friends Season 1. He first showed up as Ross' date for Monica's New Year’s Eve Party. Later, he ran off while Rachel was watching him, leading the the revelation that Marcel was an illegal exotic pet. Despite loving his little monkey, Marcel had to be sent to the San Diego Zoo when he reached sexual maturity and began humping every thing in sight.
Turns out that in real life, Marcel was actually a female named Katie. Katie had several other Hollywood roles including 30 Rock, the movie Bruce Almighty and she's also been spotted with Ariana Grande and Kendall Jenner. Not bad for a monkey.