Sgt. Carter has to be an usher at a big fancy wedding and he needs a dark blue suit to do so. He sees Gomer Pyle wearing a brand new dark blue suit and is very impressed. When he hears the price he's impressed even more. But then when he hears that Gomer bought the suit from Friendly Freddy he's not impressed at all. Because Friendly Freddy always sells them junk. But Carter is desperate and so he takes the bait and buys the suit, despite having just lectured his Marines about being careful with their payday money. Shakespeare could write a play about Sgt. Carter and Friendly Freddy. This wasn't written by Shakespeare so we'll have to take what we can get.
As you can imagine things don't go as planned. The suit falls apart at the wedding. Oops. And Gomer's suit makes both him and his "girlfriend" sneeze like crazy. They go back to Freddy to get some satisfaction.
That's the set up. I won't spoil the rest.
QUOTE: "But I was humiliated, to me that's nothing to laugh at." -Sgt. Carter.