A Weasel in My Meatsafe is an autobiographical book by One Man and His Dog presenter Phil Drabble.
A weasel in my meatsafe is a euphemism for the act of housing (temporarily) a long, thin, hairy creature within a safe, meaty environment.
Michelle - "You're looking pretty pleased with yourself this morning. What's the deal?"
Zoe - "Well, I had a weasel in my meatsafe last night, so life is good!"