This was Tom Sito's explanation for why the problem occured. The plummer has pulled Mylar (on the ground) and Jake and Edna out of the toilet. These characters once had a fairly large part in the film's story and there was a lot of animation of them already completed before the decision was made to cut the sections out of the final film.
The bottom panel shows the studio teetering on a huge mound of "shit".
Even during production we knew the film would not do very well. The animation is great but the story has far too many flaws in it. It was very difficult for us to keep up our morale for something we knew would bomb at the box office.
My own personal frustrations were mounting with quality control as we all began to slack off due to the lack of morale.
In this cartoon by Tom, he shows me working at my desk ranting about the lack of control by other artists.
"Hmmmph! That head doesn't arc! Lookit these inbetweens! Wrong all wrong, I don't know."
"You'd think I'm the only one who can inbetween here! The only one who cares! I gotta change everything! Hmph!"
"I CAN'T STAND IT ANYMORE! THIS MEDIOCRITY! THIS LACK OF ARGH!"
Tom walks in through the door and announces, "Well Brian, we can work on the Beast now..."