Yep... very popular for FP collectors. I never liked them much, even as a kid, so I never got into them. They're plentiful. They also made re-makes of those just recently.
I'm still needing a few of the old Fisher Price and Disney Action Films little movie cartridges. I'm also going to re-do some of those with other super 8's.. Like Jetsons, Aristocats, Woody Woodpecker, etc. Replacing and looping the new reel, but I have to also shorten them down.