Clutching frantically at straws here, but you're not possibly thinking of "Right, monkey", which was a catchphrase for 1950s radio star Al Read, are you?
If momick can picture it - then they'll know if it's shrek or not! I vote for Shrek - but it might have been in Shrek 2. Perhaps when donkey replies... "who you calling donkey? I'm a STALLION BABY"