Bubble Bobble (NES):
Telling a friend to beat the game by getting to the 100th level, then the game telling him that he has to rebeat the same 100 levels on a harder difficulty for a 'true win'. When he gets to the boss on the 100th level (the 2nd time though), it'll then tell him that he needs to beat it with 2 players surviving the boss to truly beat the game. lmao.
And yes, I fully beat Bubble Bobble.