Imposternator 

A person that is trying to be someone that they aren't.

Mickey: You are such an Imposternator, you copy everyone.
Carl: Yeah, sorry.

Imposternator by Camazing Person August 21, 2013

Imposternate 

A misspoken mix between 'Impersonate' and 'Imposter'. First coined in 2008 by Cameron Haskins.

V.-To assume the character or appearance of, especially fraudulently.

Tim, look! That guy is totally trying to imposternate you.

Imposternate by loki1717 October 13, 2008