Friend or Foe?

It seemed like a normal day at Gravity Falls; Mabel Pines was in the Mystery Shack where she lived with her twin brother Dipper and her great Uncles Stanley and Stanford Pines.
Dipper runs in to tell her about a new scientific discovery, and both go to investigate; it was a robotic guitarist with a titanium-alloy spine and silvery build, the male automaton was known as The Spine from the band Steam Powered Giraffe.

After their initial shock, Dipper and Mabel have to do what they can to protect their new metal friend (with the help of Pacifica Northwest).
Can they keep him a secret or will he be sent back to San Diego?

Cover made by @raindropsandunicorns :)