Note: To help refresh your memory, wiki links are provided for characters when available.
House - "Massage Therapy"
Zachary Knighton guest starred as 'Billy,' Margaret's husband. If you watched FlashForward, then you may remember him as 'Bryce,' the doctor that tried to commit suicide before the first global blackout happened.
Castle - "Punked"
The Good Guys – "Dan On The Run"
Ethan Suplee guest starred as 'Andy Davis,' the ex-governor's son that 'Dan' and 'Frank' saved when he was younger. If you watched My Name Is Earl, then you'll recognize him as 'Randy,' Earl's brother.