Radicating pidgeons is a longer way of saying rp (besides roleplay), mostly used to try to tell your girlfriend you want to roleplay but you don't want to appear annoying.
A serious, serious, illness involving having pigeonson one's head. The cure has proven to be elusive and remains highly contagious.
Ms. Bitters: There is a pigeon on your head. You've got Head pigeons. Get to the nurse before they spread to the other children!
Zim: Yes, Ms. Bitters.