Stun and catch the hidden chicken in each Scam with Ed to unlock the corresponding bonus:

Big Heads: Scam 1
Small Heads: Scam 2
Space Suits: Scam 3
Movie - Plank: Scam 4
Movie - Recording: Scam 5
Movie - Special: Scam 6

If you hit Kevin, Jimmy, or one of the Kanker Sisters they will yell at you. I like Kevin's quote "Get away from me dorks".

Get a 100% game completion by collecting all of the jawbreakers to unlock the "Unlimited Stealth", "Unlimited Damage", and "Fast Run" cheat options.

When you first enter the cul de sac you will see a bird flying around. Use Edd's slingshot to shoot the bird down. It will drop 4 of those blue health balls. I don't know why you would need them seeing as how there are no enemies in the cul de sac.