Yes, it's implausible and the ending is somewhat poorly executed, but you have to laugh when you are presented with a roomful of monkeys banging away at keyboards, one of whom is typing in Shakespeare's "Hamlet" accompanied by Edward Woodward's narration.
Vince Gilligan is one of the X-File's most consistent, intelligent and talented writers and here he makes the most of a rather wacky premise. I love how Peanuts express mails himself to the zoo, even though on reflection I realize that this is physically impossible.
I'm baffled as to the choice of title. Why choose Frohike's name over the others? Inside joke? It would have been funny to include some overt reference to Planet Of The Apes in the episode, perhaps a character named Charlton or a "damn dirty ape" line.
Anyway, the ending is a bit convoluted and seems to rush by too quickly to allow one to gain a firm grasp of what is going on. I had to rewatch the ending to see whether the action really makes sense and I'm still not sure. It just seems a stretch for dimwitted Jimmy to have understood Peanuts' plan all along such that he is able to assist in its execution.