Captain Jack - S1-E3
Trivia: The episode "Captain Jack" was the first time a toilet was shown on TV; the boys buy a baby alligator and Wally is shown putting it in the toilet tank. The network censors were so spooked by the thought of showing a toilet on television that they delayed the episode. And when the censors finally relented, the compromise allowed only the toilet tank to be shown, not the bowl.
The Return of Dr. Thackeray - S1-E35
Trivia: Steve, the cattlehand that Paladin shoots in this episode, is played by Johnny Western, who sang the theme song to "Have Gun - Will Travel."