There are few glitches related to lip tricks in THPS3. They are caused by programming errors and were fixed in the next game.
Do a lip trick then let your balance meter fall to the bottom. When it hits the bottom quickly press the button combo for a grab trick, then press revert, then do the grab trick combo again and hold the grab button. You may also spam your combo line with flip tricks while holding the balance. If done correctly it will result in you doing your trick on the ground and being able to move around while holding the trick. This glitch was fixed in THPS4 (however some have claimed they performed it in THPS4 as well).
Stuck in an invertEdit
Perform an invert trick and repeatedly press ollie button. Now you will stuck in the air. When you'll stop, the animation will be continued.
Preform an invert, let the balance meter fall up, then just watch. Your skater will stay half into the ground rotated by 90 degrees until he will stand up.