Okonomiyaki and Takoyaki in Seattle?
The only place I know of for okonomiyaki is Daimonji in Georgetown, which has four or five options. I haven't been able to make it there, so I can't vouch for or against the quality.
I can't help with takoyaki but I've seen street vendors in Beaverton set up at the Uwajimaya during festivals.
I have eaten okonomiyaki at the Harbor Steps Koji Osakaya once, about 4 years ago, but it was so far removed from my expectations of okonomiyaki that I can't possibly recommend it. My friend thought it had come out of the freezer.
Every few months I just buy myself a head of cabbage and some nagaimo, some tenkasu, make sure I still have some good aonori flakes, and grab some Otafuku okonomi sauce and some Japanese-style mayonnaise...
It's fairly easy to make good okonomiyaki. You'll just need some finely grated nagaimo, flour, and, if you're skimping on the nagaimo, some water to make a batter; add chopped cabbage, sprinkle in some salt, whatever you want to be your "okonomi mono", maybe some kizami-shouga, a bit of tenkasu, and an egg, then mix together and grill about 4-6 minutes each side on medium-ish heat.
Since I can't recreate the vibe of an Osaka okonomiyaki restaurant in Seattle, and it will likely be a few years before someone else tries, it works for me.
I believe "Kyo-fu" does okonomiyaki in Portland, though that doesn't help us in Seattle.
re: Jason Truesdell
I'd never order it at Koji Osakaya. Ick.
My Japanese girlfriend makes it for me. She doesn't use regular flour, but this stuff from Uwajimaya. It has bonito, kelp, sardine, & mackerel in it. Also adds tiny dried shrimp. Plus of course that expensive sauce. She's a perfectionist & can't get used to my electric range, never thinks they come out right, yet they're still better than anything I've had eating out. Guess we have to go to Osaka for the real thing next winter!