When you buy and go to Sid's Haunted House in Toy Box mode, speak to Rex, then get the lightning rod. You will now be inside the house. When you get all three keys, the door will open and a song will play. This is the same song that the busts from the Disney Haunted Mansion ride sing in the graveyard.
Play the Bonnie's House level on the spaceship. When you have to get the batteries in their slots, look at the sides of them. You will see a BnL logo--a reference to WALL-E, where Buy n Large is featured in the movie many times.