The show is about a boy named Russel who finds a portal under his bed leading to an alternate universe called Under. Since he is from Up and acquires the crown of Under, he is proclaimed the King. Most episodes have multiple sub-plots, and deal with the menacing Bob-Wire's attempts to steal back the crown and become the king (having to be foiled by Russel and/or his friends). Other recurring themes are Under's former king Cliff's attempts to bully Russel into handing over the crown while he's in Up (Earth), and various confrontations between Under and the neighbouring country of Near-Under. Other issues involve monster problems, and more general topics such as money, environmental issues, and even time travel.