The Lost Continent (1968)
This is an unknown Hammer Film directed by incompetent Michael Carreras.
Full of inconfortable silences, rubber creatures that actors have to wiggle themselves (think Bride of the Monster), man-eating weed, weird death scenes, uncomplete sentences in crappy dialogue that are begging to be filled with jokes.
At least check it out...
Spoiler alert: There is no continent in this movie.
There's a few movies w/ this title. MST3k 208 is a different one that the one being suggested.
Look at http://www.imdb.com/title/tt0063240/ for the 1968 Hammer / & arts film. It's a surreal mix that -begs- to be riffed.....
I don't mean to burst any bubbles, but have you seen MST3K episode 208? It's season 2 so it is lacking the obvious. On the plus side it is filled with the very needed jokes.