At least the third, completely unrelated film of this name, and likely the least well-known after 2012's party flick, and Matthew Broderick's chimpsploitation scifi movie from 1987, This one dates back to 1968, and is also SF, but of a considerably weirder nature. It's set in 2118, when American spy Hagen Arnold (George) escapes out of China - but with his memory wiped, his capture and torture, having triggered an implant designed to stop him revealing information. Now he's back, authorities are desperate to recapture what he saw, and to that end, come up with a bizarre scheme, implanting the personality of a 1960's bank-robber and setting up an entire scenario to fool Arnold into thinking it's that era. Quite how that's supposed to work, I'm not sure. Anyway, a modern girl (Baldwin) shows up and threatens to disrupt the illusion, and there is clearly also someone on the inside who is very keen that the spy does not regain his memory.
This is pretty psychedelic stuff, and would probably be more fun if you were on LSD. Mind you, so would most things. But a lot of this takes place inside Arnold's head, with animated sequences by Hannah-Barbera, and all the prodding eventually also triggers some kind of "monster from the id" (as in Forbidden Planet) which rampages around the facility, destroying people in a welter of... well, I was going to put "bad", but I think they are more just late-sixties optical effects. On the other hand, it is played considerably straighter than most of Castle's better-known work, despite the severely B-movie clear plastic helmets we will apparently be wearing in the future. [I was amused by the presence of Keye Luke, the old Chinese man from Gremlins, as the Chinese villain]
This is perhaps most interesting for the way in which Castle depicts the way he imagined the future would look back at the sixties: a slew of footage of riots, violence, war and carnage. "You’ve just had a glimpse of what’s known as ‘the good old days’," says the man in charge - and he's right. We now regard it as a time of peace and love, when that was far from the case [the raw number of US murders in 1968 was about the same as now. with the population over 75% higher] It's hard to be sure if the "present" depicted by the film is an utopia or not: while disease has been eradicated so, apparently, has much personal freedom. It feels a bit like Starship Troopers in this aspect. Unfortunately, the inside of Arnold's psyche is a great deal less interesting, and the cheapskate nature of the effects leave this floundering, particularly in a second half that largely goes round in circles.