When Raj, Leonard and Howard are playing Jenga, Raj is seen taking a block and placing it on top of the tower. In the next shot, Raj is seen again placing the same block on top of the tower.
During the Donkey Kong Jenga game, Howard places one piece on top of the pile with the Donkey Kong piece under it. It then cuts to a shot of Leonard, and there are two pieces on top of the pile. It then cuts to Howard and there is one again.
The layout of Howard's bedroom has changed. In every previous episode, the door opposite the door to the rest of the house (to the right of camera) led to a bathroom, from which Howard emerged before his daydream session in Season Four's "The Hot Troll Deviation". Now, it leads to a closet, where Howard keeps his magic supplies.
In season 5, Sheldon states that he has a fondness for Koala bears. While Sheldon is apparently not fond of biology, someone as intelligent as he is and as fond of koalas as he is would surely know better than to call a koala a "koala bear". It is a marsupial, not a bear.
Howard says Donkey Kong had Donkey Kong Jr. to teach him stuff like, ". . . throw[ing] barrels at Italian plumbers." But in that video game, Mario was a carpenter.