Pro Video Coalition:

The plan involved a sequence for the final three minutes of episode 595 (entitled “Simprovised”) that would be acted and animated in real time. The idea was to feature skilled improviser Dan Castellaneta, as Homer Simpson, responding to questions from live callers—real ones, who dialed a toll-free number—as a series of other animations played around him. The beginning and ending lines would be scripted but would still be performed in real time.

I find this an incredible achievement. Imagine an entire episode performed live.