What was the funniest misinterpretation of a game rule in your group?
Funniest? No idea really.
The only rule misinterpretation I recall was back in the days of Basic I saw the wizard XP and thought ok, he needs 2,500 to get to level 2 and then 5,000 to level 3. So I got 2,500xp, went to level 2 and erased the XP and started at 0 to work to level 3. By the time I was level 3 I had already earned close to 8,000 XP.
Not really fun I know, just kind of youthful misunderstanding.