During some of the wrestling scenes they used blow up dolls to replace some of the audience. Supposedly, they cost much less than extras and they looked real.
"Chancho" is a Spanish word for "Pig".
Esqueleto is a Spanish word for "skeleton".
While filming a wrestling scene, Jack Black jumped from the ring and struck his head on a chair. This caused a gash above his right eye which needed stitches.
Was sent to theaters under the codename "toast".
The little wrestling toy seen in the bus scene near the end is a miniature Nacho and was seen in Jared Hess's other film "Napoleon Dynamite". It is the toy that Napolean ties a string to and throws out the window of the bus.
The action figure at the beginning of the movie before we see the young Nacho playing outside the monastery is Nightcrawler, a mutant from the X-men comic. Nightcrawler was also a monk in a monastery and is, like Nacho, a character not entirely fit for his environment.