This isn't an easter egg, but still a cool reference. The events that transpire on Sakaar are a nod to the "Planet Hulk" comic storyline from 2006. The Incredible Hulk is tricked and sent into orbit after rampaging through Las Vegas. He crashes on Sakaar and, in his weakened state, is collared with an obedience disk and forced to fight gladiator battles. Hulk faces Silver Surfer in the comic, however, not Thor. He also takes over the planet eventually, becomes king, and has a child.