Some words contain two diametrically opposed meanings, i.e. aloha (hello and good-bye) or cleave (to hold tight to, to rend asunder). David has added his own word to this list: want it. His is usually accompanied by screaming and the stamping of feet for emphasis. Here we see it in context.

David: Cookie.
Debby: No, we don’t have cookies before breakfast. At least not unless I’m really desperate.
David: Want it!

Debby: Honey, it’s fifty degrees and raining outside. You need to put some pants on.
David: Want it!

Debby: David do you want the socks with the penguins or the socks with the moose?
David: Want it!