"even comedians who have a reputation for being "spontaneous""

Zactly!

For instance... Robin Williams isn't really a great 'improve' actor... he's got a GREAT memory for stuff he's thought of before... a subtle but important difference... He doenst' make stuff up on the spot.. he spends hours writing material that he then commits to memory... What's really amazing aobuot him is his 'access time' or lack there of! LOL

Ever seen a performer twice on the same CD tour? Ya got almost exactly the same show didn't ya? Almost down to word for word patter even...

That's not an accident...

But I'm telling secrets here, and I can feel the crosshairs trying to focus on the back of my head... so I'm gonna get!

:-)