Same face syndrome is an art expression for the phenomenon of illustrators having the inability of drawing faces with different features.
It is especially prevalent in relation to anime and manga series, many of which use the same style for faces, resulting in the fact, that most characters have the same visage, only with a different hairstyle and clothing.
While the exact origin of the phrase is unknown, it started appearing online following 2009, on sites like DeviantArt, Reddit and other message boards, where otakus and artist alike were discussing faults with the works of anime drawers and each other.
The expression was first defined on Urban Dictionary in 2013, with a couple other entries to follow.
After 2015, the prevalence of the phrase grew greatly, appearing on art blogs, as well as YouTube videos and Instagram posts.