I've seen the one mentioned here before about the fisherman who isn't catching any fish and then the clam tells him the reason is because he pulled out all the plants. Then the clam explicates by saying, "Everybody knows that little fish eat plants. And the big fish eat little fish. So if there aren't any plants around, there won't be any fish to catch." The guy (who previously had a hilariously confused expression) then gets it and happily says, "That means if I put back the plants, the fish will come back!" The clam says, "Right." So he puts the plants back, catches a fish and kisses it.
One I thought of today also with a fisherman that I haven't ever seen talked about here was the Fisherman Jones one. Remember how he was in a row boat and there was a big fish that he called "The wee little fishy." It was a sketch about prepositions like on, above, under. He was saying how he was in the boat and above the fishy. Then he gets out of the boat and I think goes under water to show that he is now under the fishy. Then he says, "But not for long. I'm gonna get back in my boat." Then as he tries to get back in, the fish swallows the boat whole with a big gulp. The man then says, "Ha Ha, the wee little fishy. Now I can't get in my boat, because my boat is IN the little fishy." Then I think his last line was, "Tricky little fishy." And he is sitting on top of the fish and the fish swims away with the man riding it. I know his name was Fisherman Jones because at one point he says, "The fishy treid to play a joke on Fisherman Jones." It might have been what led to his being out of the boat and in the water. I got a kick out of how he laughs after the fish swallows his boat! Maybe he only had one oar in the water.