In one episode Sgt. Carter becomes obliged to include Pyle in a Color Guard (because he's one of the only troops who will have dress blues in time) and spends most of the episode trying to find a way out of it. In the end, Carter gets enough money together to buy a uniform for a different Marine, but then Gomer comes in distraught, having lost the money for the uniform in a crap game with his friend, Duke. Realizing how much being in the Color Guard meant to Gomer, Carter breaks down and buys the uniform for Pyle instead so that he can participate.
The episode in which Goober visits, and is mistaken for Gomer by other members of the military. Goober is punished multiple times and written up, and as a result Gomer faces possible discharge because the medical staff believes he's suddenly cracked under stress. Carter is genuinely concerned that Gomer has had a breakdown. Upon realizing that it was actually Goober that was causing trouble, he's actually overjoyed.
The entire episode where Opie tries to join up. He'd had a big fight with Andy and run away, having heard Gomer's letters praising Sgt. Carter. At first Carter tries to ball Gomer and Opie out, but just doesn't have the heart to and arranges for Opie to spend the night in his own hut instead of a hotel. Then when Andy comes to get him, Carter begs him to go easy on the boy.