I think this is the first official shot of Bocce with both arms! So what happened to it? Short answer: one of the other guys knocked it clean off with a baton immediately after this shot. Long answer: short answer is a lie.
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Bocce had a friend with a very disarming smile.
Bocce did not keep his arms inside the tram at all times on the Universal Studios back lot tour.
Going back to the flashback in volume 2, I wonder if seeing the mark/tattoo triggered Bocce’s memory of training to fight Kaagan-vas.
Ha! All good potential origin stories for Bocce’s arm. Regarding the tattoo trigger, Bocce certainly has some holes in his memory, but they’ll be trickling back in as he thinks more about the KV and his past encounters with them.