American Chopper is an American reality television series that airs on Discovery Channel. The series centers on Paul Teutul Sr. (frequently called Senior), and his son Paul Jr. (also known as Paulie or simply Junior), who manufacture custom chopper-style motorcycles. The contrasting work and creative styles of the father-and-son team were the series' hallmark until 2008 when an explosive argument led to Paul Jr.'s termination and departure to start a competing chopper company. The show documents their personal and promotional activities ranging from magazine photo shoots to family holidays and custom bike shows.