Along with the okonomiyaki stand, there’s at least one sushi stand, one teriyaki/curry stand, and one stand offering octopus balls. It’s fantastic.
The first two photos are from the two really nice ladies who offer teriyaki and curry on Brick Lane proper. The last photo is from the Octopus stand, which is located on the western side of the Sunday Up Market.
I’ve checked with both and they are only there on Sundays–although the Octopus guys say that they have a stall in Camden that is open during the week. So make your plans!