According to a long-ago thread (archive.org/post/301239/is-this-public-domain) “Monsters Crash the Pajama Party” is PD. It's an artifact from the
days of live “spook shows” in movie theaters, and would have needed a big infusion of cash to qualify as “low budget.”
It’s loaded with intentional goofy humor (the “mad doctor”
character wears a lab coat that’s embroidered with “MAD DOCTOR,” for example; one
of his beakers is labeled “colored water”), and has something to do with his
efforts to turn the teen cuties into gorillas.
Apparently, the doc’s laser cannon was supposed to blast a hole
right through the movie screen, thereby freeing the monsters to roam through the
audience and steal another subject for his experiments.