The other day, I was playing Zap's heroic challenge with Chop Chop. When I destroyed a cat statue with the sheild stab (hold your sheild, the use sword), Chop Chop carried on moving. When the short cutscene was over, Chop Chop moved at Super Speed!
Yea, it happens with some melee characters I've noticed...I think Slam Bam ends up walking to the water and starts to surf away at a few points... It's kind of funny although if that challenge weren't so darn easy, I'd probably hate that it happens.