Factual error: In Cerulean City, there's a man that will trade your Poliwhirl for a Jynx. After trading, he'll say "The POLIWHIRL you traded to me went and evolved!". He may be referring that the trade evolved his Poliwhirl. While there are Pokémon that evolve via trading, Poliwhirl does not. This is a translation mistake from the Japanese Red/Green version, using the Japanese Blue text.
Dr. James
24th May 2011