Isn't it funny

Tuck has dozens of original knock-knock jokes.  Most of them end with the word poop or diaper, and they all need a bit of work, but he delivers them with confidence, and often with fits of giggles before he can even finish.  We laugh politely, and remind him which words are not appropriate outside our own house.
Tollie's begun trying his own hand at telling riddles, but he's usually the only one grabbing his gut at the punchline.  When Tucker admonishes Tollie for using potty words, Tollie argues But I learned them from you, Tucker.  

The boys laugh at each other's toots.  And burps.  They laugh at Looney Toons and at the trick can of party nuts.  Everything is silly.  They're both, usually, moving at a hundred smiles an hour, like they don't even know how to have a bad time.  Sounds of delight spill from the places they play, and the cheerful racket the two of them make together creates the surest joy in me, noise I can almost breathe like air.

Sometimes they belly laugh, the side-splitting doubled over cracking up kind, so hard there's no sound at all.  I like that too.