While this is a little bit of a subjective question, there is a rather definitive answer. While this Pokemon was always likely to be admired by the Pokemon community thanks to its cute and colorful aesthetic. The reason why so many fans took to this objectively rather weak competitive Pokemon is because of the original Pokemon anime series. Jigglypuff was known as a rather charismatic, jealous, and sassy Pokemon, which led to great viewing and usually some characters covered in marker ink. So we reckon this Pokemon’s mass appeal is largely down to its personification in the anime series.