You pay
less to retreat your Jigglypuff, Wigglytuff, Wigglytuff ex, and Igglybuff. (Poké-BODY)
Baby Evolution - Once during your turn (before your attack), you may put Jigglypuff from your hand onto Igglybuff (this counts as evolving Igglybuff) and remove all damage counters from Igglybuff. (Poké-POWER)