Justin plays Mario Kart Wii often on Troy's channel. His profile shows that he has completed all cups in first, implying average to above average skill.
Justin's most prominent series on TWD98 is easily Rate That Custom Track, in which Troy plays a track and Troy and Justin subsequently rate the track on a 1 to 5 scale (although he sometimes gives pretty weird ratings). Justin has appeared in all videos in the series.
Justin has only played Mario Kart 7 once for Troy's channel. In the video, Justin played both Rainbow Roads in the game against his will, only agreeing to do so because he drove in a boat, reminding him of yachts. Mario Kart 7 was also a prominent element in one of his attempts on the Game Show Shortcut Challenge.