Reggie Van Dough is a character from the Richie Rich comic books, and as such, he is also the main antagonist of Richie Rich's Christmas Wish. He is the cousin of the protagonist, Richie Rich. He intends to usurp Richie's title as the richest kid in the world. He always threatens to get in a very bad mood when he doesn't get his way, and he badly treats his servants.
In the movie, Reggie is the one who steals a remote to get Richie framed for a crime and lies to make him feel like everyone would be better off without him. In the alternate reality, Reggie is adopted by Mr. and Mrs. Rich, and he mistreats them too. He also owns Richie's dog, Dollar, who recognizes Richie even then. Eventually, Reggie's servants quit on him, and Mr. and Mrs. Rich send him to his room as punishment before Richie wishes himself back.
Back in the real word, Reggie tells Richie that he sabotaged the event. Richie realizes that he wasn't his fault and he made that wish for nothing. They forgive each other.