rush_(mega_man)
A multipurpose dog robot created to help Mega Man (character) by Dr. Light (mega man) and introduced in Mega Man 3.
It has a spring to help Mega Man jump to hard-to-reach platforms, it can transform into a submarine to facilitate movement underwater and transform into a jet for quick stage traversal, among many other abilities.
It can also fuse with Mega Man, turning him into Super Mega Man (mega man).