Tarzan is spoofed. Another is a play on Don Quixote, with our protagonist teaming up with a Don Quixote type who fears Russians and sees bad guys everywhere. Another story is a spoof of Superman called S*perm*n (I'm not sure if that's supposed to be funny because it looks like Sperm-man).
I'm not a fan of the old Mad magazine (or more recent ones, for that matter) as I find the humour to be dated. This book, however, had plenty of truly funny bits. Tarzan gets pissed at Jane for not wearing a bra, so she takes her skirt off and ties it to her chest (leaving her bum and vagina exposed) - it's really funny visually, and isn't obvious.
That being said as many funny bits as there are, there are just as many failed attempts (perhaps just dated). The stories don't seem interesting enough to stand on their own.
Ultimately, it was a decent book and I will be checking out more of Kurtzman in the future (if only because of his reputation).
eBook Goodman Beaver