Is how when they want to come inside after being in the backyard for awhile, instead of yelling at me, calling for me, or just plain banging on the door, they stand there side-by-side sweetly pretending to be doorbells, going 'Ding Dong! Ding Dong! Ding Dong!'.
They truly do love sound effects. I think 90% of their language is made up of sound effects. For such a long time, everything they said was an immitation of our intonation. No words, just 'uhhhh' with the correct ups and downs in their voice, so we knew what they were talking about.
We knew they were saying such things like: 'my turn' (me me), '*I'm* being good', 'I didn't do it -HE did it!'....
And the sound effects: a Big anything is 'Hooowaaaah!'. A little anything is a 'baby' (like hooowah tree, baby tree). Trains are 'dootch dootch', cars are 'beep beeps', cats are 'meow', horses are 'neighs', cows are 'moos', etc...