I love clowns... if they have original material. The circus that comes to town every year has used the same clown acts every year for the last four or five years. I've lost count. If they have fresh material, they're hilarious, and I have absolutely no idea how people could possibly find these delightful comedic experts to be creepy.
Ventriloquism... well, one of my favorite comedians is Jeff Dunham. Haven't been able to find any other ventriloquists to be entertaining, though.
I've never seen the kinds of mannequin's you're talking about; at least, not outside of cartoons. The only mannequins I know of are the ones that display clothing in the windows of shops at the mall.