Children Love Pokémon (and Pokémon Centers)!
Pokémon needs no introduction. But just in case you've been living under a rock in a cave for the last two decades, it is Nintendo's media franchise created in 1996, which has gone on to become their second-most successful character in history.
What not so many people know, however, is that there are eight specialty "Pokémon Centers" across Japan where you (ahem, children) can purchase Pokémon character goods - from stickers and badges to foods and stuffed dolls to clothes and many other rare/hard to find items. These centers are located in: Sapporo, Tohoku (Sendai), Tokyo, Tokyo-Bay (Chiba), Yokohama, Nagoya, Osaka, and Fukuoka.
Not only are they wonderful places to take children to and let loose, providing a bit of rest and relaxation for the parents (until it's time to leave and pay the bill, that is), but the goods the centers carry make wonderful souvenirs - and will make *you* look like the coolest gift-giver to the folks back home.
Pokémon Centers often have special events and "guest appearances", making them much more than just a run of the mill character goods store. Even if you have no interest in Pokémon, they're still interesting places to browse. I visit the one in Yokohama's Landmark Tower whenever I'm there, and I always leave with a smile on my face.
For store locations, maps, and access information (in English):