A tribble is a fictional creature from Star Trek. I shouldn't have assumed you would know that, sorry. It's just that they're from a well-known episode. I have a stuffed tribble. It purrs when you hug it!
Marvin is my favorite, too. I named my pet tribble Marvin, and I made a Marvin costume for Halloween last year. It was based on the new movie style. I prefer the old version, but it was a much more difficult-looking design.