can anyone remember?

A cartoon from years ago,
a human child living in a odd town full of monsters and he's friends with a vampire kid and in one episode the vampire cousin comes over in a hot air balloon, which is odd because all of them can fly except her, something happens to the little vampire where she needs to fly but she can't and the human ahd the small child go after the little vampire in the hot air ballon and it is then revealed that she's afraid to fly and she says, 'if anda say anything ill suck your blood', while they are laying down on a roof top, and they both burst out laughing.