Toss blackcats or m-80's into the muffler, have to throw them in far, when the car gets so hot, they go boom! Like so... Also you can scoop up a doggy doo and stick it in the air vents.... make sure you only do that one in winter time when they have to use the heater hehehe. Another fun one is to duct tape a kids sqeeze horn to the muffler tip. When they start it, it goes quaaaaaaaaaaaaaaack.... that is funny. Only works on 4 bangers, 8 cylinder cars usually blow it off the muffler in short order haha.