“We are from the planet DUPLO and we are here to... destroy you!”
The DUPLO Aliens are giant creatures that appear in The LEGO Movie. They are mainly built out of DUPLO pieces and come from the planet DUPLO. The Lead DUPLO Alien is voiced by Graham Miller.
The LEGO Movie
Spoiler warning: Plot or ending details follow.
They appear at the end of The LEGO Movie after Finn's father, "The Man Upstairs", states that Finn's little sister will be allowed to play with the LEGO as well. They are beamed down from a ship into Bricksburg and announce their intentions to invade. It is possible that they were defeated after the movie, or the story will continue in The LEGO Movie 2.
Spoilers end here.
Those hard of hearing and/or unfamiliar with the brand believe that the alien (or child voicing it) says DUPLON rather than DUPLO.
The DUPLO Aliens scene was cut from the video game.