As the ghosts are helping Alan get into the reindeer costume near the end of the film, the Ghost of Christmas Future has the jingle bell collar hanging from his arm, but in the next shot it's already around Alan's neck.
Near the end of the film, as Steiner is running towards Alan during the concert, he passes by the ghosts of Christmas Present and Future twice.
Roscog uses Allen's Christmas lights to run his snowblower. Holiday light cords are equipped with inline fuses to protect the bulbs from power surges and would not be able to power the snow blower.