Something keeps hitting my hood!!!

Well, sorta...Heres the situation. Everytime i turn off my car i hear a thump from above...I have no idea what it is, it's not really a big deal, just a bit of a annoyance...Oh keep in mind my sunroof is broken, thats really the only thing i can think that could do it...but whats up there that would do that?!?

Thanks in advance