While we're waiting for Shout! Factory to release the eagerly anticipated 4 CD "Box of Danger" in late April, I just stumbled across a FST release from 2003 that I had never heard about, called "All Things Firesign", which is a compilation of the best bits the 4 or 5 Crazy Guys did for NPR's "All Things Considered". Highlights include some adventures from Mutt and Smutt, along with a couple of Nick Danger bits...
Here's a nice Firesign Theatre timeline, followed by an interesting interview.
And a Japanese music group called "Firesign"