I cracked open a couple of these back in college, and tried to do some crude telecine experiments with them. Never saw any alternate takes. The only unique element were the title cards Kenner made for these.
The insides of those film cartridges is a maze of plastic gears and guides, which wear the heck out of the film loop they contain.
I know Kenner made one for Alien, but did they ever make any for Empire?