How do you get photos in pokemon games?

How do you like get pictures of you, animals, fake pokemon, etc. in pokemon games? Do you need action replay? That I have. Beacuse I saw videos of like Mewthree and John Cena in the pokemon game. So, it must be possible, right?|||It's all On the computer you need a rom player editor and a pokemOn rom they are very hard to do you need to search on you tube how to edit romshttp