A technical assistant in a lab, particularly one that works with mice.
"Professor, how did you become so rich, famous, and wise?"
"I began, like you, as a humble mouse wrangler ..."
A mouse Wrangler is a guy that surrounds himself with inferior and weaker males as his primary friend group in order to make himself seem tougher and stronger than he really is. The typical mouse wrangler will rule his mice fiefdom with an iron fist of intimidation, the mice will even talk this individual up as they have come to accept him as their supreme leader.
This particular individual will generally be seen as a bad-ass amongst his friends the mice. But will readily shun and avoid conflicts with true alpha males that would inevitably whoop his ass. As taking an ass whooping would cause his kingdom to crumble and the mice would adopt a new leader.
Hey, that Dude sure is a Mouse Wrangler, look at all those pussies that hang out with him and worship him like he's top dog.
I sure would like to whoop his ass, but he keeps duckin and dodgin and hiding behind his friends who think he's bad. What a Mouse Wrangler.