Well the Charr dance is actually a native dance from New Zealand. The dance for the Charr wasn't released till the last stress test so if someone wants to call out being copied I think it is NZ that should be calling it out. Rengar is actually based on Predator, read his history. They couldn't put something that looked like one as the art wouldn't work and he'd have been scrapped, the only thing that is the same about Rengar and the Charr is that they have feline qualities.
Rengar's only means of escape is to hope there are enemy minions to hop on if there is a bush around, or hope that you have five ferocity to root one of the champs chasing you.... So yeah his escape is all about luck, but depending on your build you can stomp 5 champs.