From Season 1 Episode 1. Adrian Monk's (Tony Shalhoub) keychain is a silver "T", it belonged to his late wife Trudy. Adrian is at a funeral for a case, he is sitting in a balcony. He misplaces his keys but finds them in his pocket. He is so happy he is swinging them on his finger but they slip and fall into the open casket. He tries to fish them out unnoticed with dental floss and a paperclip but fails in hilarious fashion.
From season 1 episode 6. Adrian is investigating the death of a billionaire who tried to mug a man. The victim of the mugging has a keychain with his college fraternity on it Phi Beta Tao. This becomes an important clue later on.
