What do do on a rainy day in Tokyo?

The Mori Art Musuem at the top of Roppongi Hills. Nice views, nice gallery, plus cool city models of New York, Tokyo, Shanghai, etc

It ended up not raining in Tokyo (well, it was a tiny bit drizzly on Saturday). If you're willing to share, what did you end up doing? (I for one took my own advice, going to both Shinjuku and karaoke!)

http://www.namja.jp/, in the aforementioned Sunshine City in Ikebukuro. It's a somewhat creepy indoor amusement park with (separate) ice cream and gyoza-themed eating areas.

Tiresias: Hong Kong and Shouwa themed I do believe those are inside http://www.palette-town.com/. The station I would take for that, and Odaiba is 'Tokyo Teleport' on the rinkai-line.

Oh, also, the (free) view from the Tokyo Metropolitan Government building in Shinjuku is incredible.

I've taken that boat ride --- you don't have to sit on the outside upper deck if you don't want to, although sitting below kind of defeats the purpose of the boat trip (not the most picturesque, truth be told --- it just looks like Tokyo, as seen from the river.) Odaiba by itself could be a decent excursion. I forget the name of them, but the Hong Kong and Shouwa themed malls where the boat lands are pretty entertaining in and of themselves. Can't remember the name of the station off the top of my head, either, but I'm sure you can easily find it.

Ok, these are some good ideas, thanks. Had the weather been better I was planning on riding from Asakusa to Odaiba via the Sumida River on a tour boat of sorts... has anyone ever done that before? Would it still be worth doing even on a somewhat rainy day? The boat is covered, but I'm wondering if the view might not be so good in the rain.

Odaiba mall is fine, which is where Joypolis is. Across from Odaiba is Palette town. More Mall shops, but also large car exhibition hall, with ride-in car things. Next building to that is a large arcade hall. There are endless bowling/dart/pool/arcade places around everywhere. Like http://www.shibuyaest.co.jp/index2.html in Shibuya. There are the even larger places like that out of town a little, which had air-cannon battles etc. I fail to remember what it was called though. Round1? (Kid's area was reserved for drunk adults at certain times).

http://tokyo-joypolis.com/english/index.html http://tokyo-joypolis.com/english/index.html#howtoget. http://www.leisureland.jp/. http://www.megaweb.gr.jp/index. http://www.ooedoonsen.jp/higaeri/english/index.html (though if it's a date, I guess this one's out). I used to frequent Odaiba, can you tell? Oh, and if you've never been, going to the top of http://www.tokyotower.co.jp/english/ can be a fun experience (did you know that about a third of the steel that makes up the tower was taken from US tanks damaged during the Korean War?). Besides the view from the top, which might not be so great on a rainy day, there's a really cheesy wax museum on the third floor if you're into that kind of thing.