In one segment, Brittany the dumb cheerleader walks down the hallway giving her friends extravagant gifts. She explains why to Tina:
Sam and Brittany start a Mayan Apocalypse Club to tell the others how they feel:
After a song-and-dance number, Sam proposes to Brittany and she accepts. Coach Beiste says she can marry them because she was ordained on a Mayan church website. She performs a marriage ceremony on them.
Four days later, the world hasn't ended and the couple faces the reality of being married. They go to the coach, who clues them in.
COACH: There aren't actually any Mayan church websites. The Mayans were wiped out 500 years ago by the conquistadors and smallpox.
SAM [to Brittany]: That's like chickenpox but smaller.
It's silly for Sam and Brittany to believe in the so-called apocalypse...but they're silly characters. Within the context of their misguided belief, they're sincere about the Maya religion and culture. They treat it with respect, not as a joke.
The only real mistake is the coach's. The Mayan civilization was "wiped out"--i.e., gradually abandoned--but the Mayan people continue today in Guatemala and neighboring countries.
All in all, it's another good TV bit. The apocalypse idea is raised only to be dismissed. Instead of scary doomsday talk, there's genuine Maya lore. The only false note is the coach's claim that it's ancient history.
For more on Glee, see Comanche Sue in Glee.