The Clampetts mistake Grunion for surfers, but they have talked about surfing before on the show. Why did they forget what surfing is and think that these surfers are Grunion who are "poor sailors?"
Goof: When Granny is looking out at the "Grunion," actually surfers, she says "Oops" before the surfers fall off the boards when she should say it after they fall.
Granny: Put down the vittles.
Jethro: They won't be safe.
Jed: Put em down boy.
(Jethro puts them on the ground)
Jed: Now they's safe.
Helen: One word from me to Mr. Clampett and your goose is cooked.
Drysdale: That's blackmail! You know, you have a very unscrupulous side to you! I like that. We could work very well together.
Granny: Would you like some gravy?
Surfer Boy: Groovy!
(Granny heads up to Jed)
Granny: On the island of Grun, they call "gravy" "groovy."
Elly: Them Grunions must be dumb as Jethro.
Jed: Elly, if Jethro was to take his brain to the isle of Grun, they'd make him king.