Disclaimer- I really don't think I want to own Harry Potter. It would be really annoying putting up with him all the time.
Peeves had gotten tired of doing the same boring pranks every year. He didn't know any new ones though. The marauders taught him. That's why he never turned them in. The Weasley twins taught him more, so he never turned them in.
But would they ever compare to Harry James Potter, who somehow managed to singlehandedly teach Peeves every muggle prank in the book?
Peeves knew a few. He learned more each time a true prankster came. But Peeves couldn't cast magic. He could only manipulate the material world.
And Harry had spent years with muggles just like him.
And that is why, after so many years of always being able to catch the culprit nearby, Snape got gooped, repeatedly, by Peeves. Because Harry showed him how to tie the rope.
And somehow, Harry knew that Dumbledore would never tell Snape.
But, the green goop did look particularly fetching on him.
A/N I was thinking about that. Peeves can't cast spells. So, he can only do a few things. Harry tells him muggle pranks in exchange for freedom to travel unhindered.