Retromimesis (also known as retromimicry) is a type of spell that was used by Papa Smurf on Gargamel in the comic book story "Smurf Vs. Smurf" (and also in the cartoon show episode "Romeo And Smurfette", though in that story it didn't have an actual name) that caused the both of them to exchange appearances. The spell required both of the participants to lock eyes on each other while the spell caster recites the spell to activate the transformation.