USA Today reports from the Con::
... Futurama's season finale will feature three different cartoon formats ...
... Simpsons' executive producer Al Jean said the show's writers have no specific concept for a finale episode. ...
In Family Guy's season opener, "lottery fever hits Quahog and the Griffins strike it rich," creator Seth MacFarlane said. He [also] said there will be a Family Guy movie
What I can tell you about T.V. animation is, there's a lot of squeezing of schedules, and much pressure put on the artists working in it.
The standard mantra (more or less) is: "We don't have money in the budget for overtime."
It's assumed that employees will hit their deadlines come hell or high water, and not bother production managers' beautiful minds with icky things like authorization requests for extra hours. If more time is needed, the expectation is that everybody will do it on their own hook.
And many fulfill that expectation.