I was in a pool with Lulu, and she was holding on to the edge of the pool.  I went next to her, blocking her path, and said “None shall pass until you answer the riddle”.  Then I gave her a riddle: “What is larger, an elephant or a mouse”?  She said elephant and then could pass.  She was delighted!
The real tests of a game are whether she requests to play it again (which she did!).  In fact, this game got her highest praise, of playing it herself asking her mom which is bigger, an elephant or a baby elephant (after blocking Mommy’s path)!