You know what I am talking about. Happened in Ren & Stimpy. I can even recall some instances on Spongebob Squarepants. Someone is shown to be disgusting in some way or another, but the animation quality doesn't quite cut it, so they have a regular old drawing thrown up on screen for a few seconds, usually with a horror scream or Massive Odor soundbite. The detail is horrendously deep, showing all the fine lines and nasty bits that the standard quality when animated cannot show.
I looked all over the Animation Tropes and couldn't find this but it might exist already.
Needs a better title, needs examples, needs a better description, etc.