Bob was initially a wild flower alien, before he was caught by Dan the Cyborg in 2009. Dan proceeded to train him like a pet, and he eventually became considered (by Dan, at least) to be a member of the team (much to Liam and Ben’s reluctance).
Bob died in 2010 sacrificing himself in order to save Dr Robin Turner from a rabid Flower Alien.
X.1 Earth’s Guardians
2.1: The New Member
X.1-2.1: 4 Episodes