Mumford & Sons are a British rock band from London featuring Marcus Mumford, Ben Lovett, Winston Marshall and Ted Dwane. They are notable for incorporating both modern instruments with traditional folk instruments, as well as their original look in 18th century-style garb.
In "Peter, Chris, & Brian", Peter vows to make Chris a success just like Mumford did with his son. As the young son starts to leave the 18th century-style home, his father calls him out for not using the proper look, and encourages him to write songs that sound the same every time.