\I'm not sure if he can be considered a cartoon character, but The Count from Sesame Street has scared the pants off me since I was a kid. I once had a dream involving me, being chased by him down my crowded street, screaming at the top of my lungs and know one noticed. I ended up hiding in my babysitter's house and heard him come to the door asking for me. I woke up before he found me. I was slightly traumatized and still cringe when people begin counting and laughing in an imitation of his deep voice.
1...hahaha....2....hahaha....3... *shudder*
 
Strangely enough I'm still fascinated by vampires. I'll have to look into this a little more.