Bikers are a recurring enemy in the Ninja Gaiden series, starting with Ninja Gaiden (Arcade).
Ninja Gaiden[]
Bikers are the first enemy encountered in the game, first appearing in Act 1-1. They slowly march in one direction, swinging their bat every now and then and turning around if they reach a ledge/wall. They only deal 1 point of damage on contact, and are easily defeated in one hit by any attack.