Mega Man's loyal robotic dog is named Rush. Created by Dr. Light, Rush first appeared in Mega Man 3 and became one of Mega Man's most recognizable support characters in the Classic series.
Rush is more than a standard canine companion. His adaptable design lets him transform into useful equipment, including Rush Coil, which launches Mega Man to higher platforms, and Rush Jet, which lets him fly across gaps. Later games added forms such as Rush Marine, a submarine, along with motorcycles, drill vehicles, and spacecraft.
Players sometimes mix Rush up with other Mega Man support characters. Beat is a robotic bird, Tango is a robotic cat, and Eddie is a support robot shaped more like a mobile item dispenser. Rush's name also has a small piece of Capcom history behind it: it was inspired by The Speed Rumbler, known in Japan as Rush & Crash, and resembles the pronunciation of “Lassie.”