That was a prank by his boss, co-workers, and Judge Memnok the Mind-Taker for his birthday. A very, very long prank (I THINK it was revealed on his next birthday…may have been multiple years, though. Was definitely perpetrated and revealed on his birthday.) It was episodes 7 and 8, and was the first appearance of Blue Falcon, who has been a recurring character since.
As far as I can tell, the show’s not cancelled. There’s no new episodes listed on tv.com since October (episode 32, aired October 23), but it just has an odd schedule - this season started in July (with episode 23).
Anyway, great. I do like Birdman. I was afraid they may have cancelled the series and decided to go out by killing off the main character, which always irritates me.
He was in jail for over 5 years and was taken to the chair on his 40th birthday, IIRC. Then the gag was revealed. The awkward silence about his prison marriage was funny.
They just finished a new season a month or two ago. From what I can tell on the Adult Swim website, the one with Birdman getting the chair was episode 8 and they’re now all the way to 32 episodes. The most recent season is by far the most sophisticated and, imho, funniest. Birdgirl rocks!