Continuity mistake: When Walter and Danny are trying to show Lisa what the Zathura game does, Walter lays the "Promoted to star ship captain" card on the game board in front of the card console. Two shots later the card vanishes. The camera had only changed for two seconds, so it's unlikely that either of them had enough time to take it away.
Continuity mistake: Danny has plasters on his right elbow. During various scenes, they appear and disappear. Also they once changed design. And around the end of the movie, the plasters disappear from his elbow and appear on his right hand.
Continuity mistake: In the opening scene, when Tim Robbins is playing catch with his son, the cars in the background keep appearing and disappearing.
Continuity mistake: When Danny and Walter are in the kitchen, the zorgons shoot at them and blow out the kitchen windows above the sink. Later when they go back into the kitchen to start a fire to bring the zorgons back, Lisa goes into the kitchen and the windows are not broken.