Leonard Nimoy's first role as an alien.
There's a 30 second shot in the credits where Nimoy (I think) is walking underwater. He also was an occasional guest star on "Sea Hunt" so he obviously knew about scuba diving and breath control. As a little kid, it kind of freaked me out that someone was obviously walking underwater without seeming to get air from anywhere. Kind of impressive!
I see that Turner Classic Movies is showing "THEM!" on Monday.
A tiny role for Nimoy.