The Boys from Brazil is pretty funny to watch now. I think I remember it as being a serious thriller back when it came out.
Gregory Peck and Lawrence Olivier are kind of in a competition for who can do the most over the top overacting. Peck plays the sadistic Josef Mengele, and Olivier plays a Jewish Nazi hunter. Olivier's accent is just too much to bear.
The plot, for those who don't know it, concerns a conspiracy that has cloned Hitler. About thirteen years earlier, Mengele created a bunch of Hitler baby clones and distributed them through adoption to families all over the world where the father was 50 years old and a civil servant, and the younger mother was presumably likely to be doting. Now it's time for the fathers to die in accidents, and Megnele convenes a bunch of secret evil Nazis to carry out a mission. They meet at his home in Paraguay where he has a kind of Dr. Moreau thing going on. Unfortunately the plan begins to fall apart as Olivier begins to figure it out (based on a tip provided by a young Steve Gutenberg).
Anyway, it's all good fun. The 13 year old Hitlers are great.