Tarzan, the Ape Man

Although the frank sexual dynamics of this movie are what make it interesting (as well as the genesis of the Tarzan yodel), the amazing thing is that it was written by Ivor Novello. Surprisingly well-preserved, the action is good although the cottonwoods on some California ranch sure get a workout.
The costumes for the great apes are not one whit less believable than those used in 2001: a Space Odyssey. They even use a chimp for a baby great ape.
It's probably addressed satisfactorily somewhere, but why is the chimp named Cheetah? Is there a cheetah somewhere named Chimp? And when Tarzan calls for Cheetah, why don't cheetahs respond?