A Frightened Hound Meets Demons Underground - S1-E14
Stupidity: The bad guy is dumb enough to stay in the basement of Captain Sally's instead of taking his loot and fleeing.
The New Original Wonder Woman - S1-E1
Stupidity: There's much fuss about who will take Steve Trevor back which is resolved via a contest. Why the Amazons don't heal him, if possible, then set him adrift to a safe port is never asked. They did this when Nazis invaded in the two part episode The Feminum Mystique.
Stupidity: With about 5 minutes left, the Black Sheep fly towards a Japanese carrier. They are flying Japanese planes. The Japanese spotter speaks in Japanese. The translation on the screen says "There ours" instead of "They're ours."