Arthur and company enter the cave, where they find an Aramaic inscription carved on the wall by Joseph of Arimathea. It starts by describing where the Grail can be found.
Unfortunately, the description ends in "aaarrhhhhggg." Looks like ol' Joseph kicked the bucket in mid-carve.
To make matters worse, a horrifying beast appears. It has tons of eyes and eats Brother Maynard and chases the company around the cave.
Things look dire for the company but fortunately the animator has a heart attack and the monster ceases to exist.
The Fourth Wall isn't so much a wall in Python movies as it is a revolving glass door.