I flew a checkride with a guy who left his gear down after a low approach. We flew back 40 miles with the gear down. I kept commenting on what a dog the aircraft was, and how slow it was. He never got the clue till it was time to put the gear down for landing again. DUH it is already down!
Typically heard on a submarine's first underway after a few weeks inport:Old joke: What's the second sign you've landed gear up? It takes a lot of power to taxi...