Astolfo Effect

A phenomenon where a historical (or otherwise original) figure gets overshadowed by its version from modern culture. Named after Astolfo, who is originally a character from a French legend, but most people nowadays know him from the Fate anime franchise as the guy who looks like a girl, also referred to as trap or femboy.
Most prominent if you try to look their images up. There are even more famous examples, such as the infamous dictator Nero Claudius.

A: I tried to search for some pictures of this guy for my school presentation but all I could find was this anime girl for some reason.
B: Yeah, that's the Astolfo effect for you.