OK.. so my girlfriend just found an annoying glitch due to incomplete code in Lego Harry Potter: Years 1-4 for xbox 360.

In the courtyard facing the clock tower you get a broom. If you take the broom through the arch way behind the pendulum and all the way up that back wall, you'll jump behind the background tiles and fly to other sections of the game.

Unfortunately I cannot take screen shots to show what I'm talking about.

In one instance she ended up behind the background tiles near the Herbology building. The game recognized her near the door, but kept bucking her off of her broom thus getting stuck in a death loop. We had to exit to Diagon Alley.

If you get frustrated easily, don't try this.
If you have not saved in a while do not try this!

It totally reminds me of old Mario 64 glitches.