I mention this just for historical context, not because you should be expected to know everything that happened in Seattle before you were born--but when Annex Improv was active, they did long-form improv similar to Del Close's Harold. They probably weren't the only one.

But because the internet didn't exist, you sort of had to be there.

I remember in the 90s the Stranger ran a big review all of the improv groups--and there were a ton of them. Who remembers King's Elephant?