Riddle: (This one is harder is you tell somebody orally.)
These are the things behind the green glass doors:
Kittens but no cats; Puppies but no dogs; A roof but no ceiling; A floor but no ground; Walls but no windows; Cartoons but no Anime; Food but no cake.
What do everything behind the green glass doors have in common?
Answer: The words all have double letters.
(You can use any words that are alike, but one has to have double letters. Mommy but no Mom; Books but no magazines; etc.)