Donnie was the mechanic for the Westside Rollerz in the original Saints Row game, and in Saints Row 2, he is The Brotherhood's dedicated mechanic. Donnie had a crush on Lin, and after William Price killed her, he left the gang. Donnie supposedly made custom parts for the Rollerz cars, evidence of this is the cutscene in the first Rollerz mission, where the guys are inspecting Lin's Voxel. One of them says 'That spoiler looks like Donnie's work'.
Donnie returns as a member of the Brotherhood
in the sequel
, in which once again, he is the only named character in the gang to survive.