The maneki neko is a traditional Japanese good luck symbol. It looks like it's waving, but it's actually doing the Japanese beckoning gesture. Supposedly, beckoning with the left paw means, "come here, potential customers!" and is often seen at store entrances. The right paw, meanwhile, means "money money money!" and is usually spotted at home or at pachinko parlors.
For the kid, though, these solar-powered maneki nekos mean "we're next door to the post office." There's a gift store in our DC neighborhood that's slightly Hindu [it's run by a Western woman in a sari, and has more consciousness-raising swag than the average Hallmark store], and there has been a rotating rainbow assortment of these Hidamari no Tami ["Sun People"] toy cats waving from the display window for most of the kid's waking life. Every trip to the post office has to involve a visit and greeting to the relentlessly waving army of good luck kitties.
I guess you could buy just one, but trust me, the effect is better/creepier when you have 8-12 in a row. Very Kitties of The Corn.
They're for sale at Jbox.com, a specialist in kawaii Japanese kitsch, for $16.50 each. [jbox.com]
Otherwise, it's the hippie gift shop in Cleveland Park next to the movie theater. You'll figure it out pdq.
Aw, how cool are you? The cheesy Express paper picked this up and quoted you in their "we're trying to be hip" section of Thursday mornings edition...how fun to come across it on my way to the soduko and think "pshaw, I've already seen this!"
[which cheesy Express? I love to collect examples of my public humiliation. update update: ack, someone just called. It's the free paper for subway riders in DC. -ed.]
...And I'm so cool, I posted twice! Just to redeem myself, I must point out that I spelled "sudoku" wrong in the first one and didn't think it had gone through yet...