Well, I've been looking for some it's-so-bad-it's-good German covers for a while, but mostly they were just it's-so-bad-it's-bad. And my standards were high. I mean some of those Japanese covers are just good, period.
I finally found two at a recent flea market. Crazy type, weird pictures of the musicians, wacky colours—all beautifully composed.
Wikipedia has some information on the Dutch entertainer Rudi Carrell.
Even the German Wiki on Horst Muys is very limited.
Maybe the covers are so fun because they were both kind of into comedy.