https://m.bulbapedia.bulbagarden.net/wiki/List_of_Pok%C3%A9mon_with_gender_differences
I've recently learned pokemon have difference depending on sex.
Topic: How often do artist not know the difference between male and female pokemon?
Posted under Art Talk
the male/female pikachu difference is probably the difference that's most prominently featured in fanart, but the other ones do see a decent amount of representation, at least for the ones that aren't just "slightly larger/smaller/longer/shorter <thing>".