Which is actually a lot more helpful than it sounds, since one of the most unnerving things about the fear in question was the fact that I never knew where it came from. This seems the most likely answer and (like Who Framed Roger Rabbit?) it means I've something concrete to watch again one day with someone to hold my hand and hopefully get over it.
Still don't think I'm ever likely to stop finding Mr Punch scary, though. Ah well.