Borderlands: The Pre-Sequel is a game that doesn't take itself too seriously, and it's not ashamed to poke gentle fun at other games either. There are several Easter eggs for gamers to find, but the Super Marios Bros. one is probably the best.
On the last level in the game, there are several elevators that smash players into a ceiling, but one of these elevators leads to a black hole, mimicking Super Mario's famous pipes.
Inside you can find an area that is an obvious reference to Nintendo's classic. If you want to find more about this Easter egg, check this video on Youtube. After that you should also check our Borderlands: The Pre-Sequel review, as there's more to the game than cool Easter eggs.