I spent a couple weeks looking for "Mighty Joe Young," the big gorilla movie Ray Harryhausen made in 1949 with his idol Willis O'Brien, originator of the original Kong.
Finally found a copy for a reasonable price, in a boxed set, that also includes the original Kong and Son of Kong.
Joe Young isn't really a Kong movie, the gorilla is almost normal size -- but the animation, OMG it's realistic. Harryhausen really makes the puppet come to life. There are so many optical tricks to make the stop-motion tie into the live action that it is very easy to suspend disbelief. Wonderful, wonderful production. Lots of humor too.