"pig" referring to the 50's slang term for police;
the automatic instant reaction when you see a cop to put your foot on the break and act unsuspicious
Friend 1- "dude why did you just slam on the breaks when we passed the cop?"
friend 2-"sorry my pig reflex was acting up."
Not exactly a reflex, but it's a term used to describe the phenomenon of feeling sleepy after eating a heavy meal.
Once I cleared the buffet table, my pig reflexes were acting up.