With over 800 Pokemon out there, the series has seen an incredible variety of creatures, from the cute to the rugged. There are some crazy details behind some of the most iconic Pokemon, and they aren't all as cute as they appear.
The truth is that Drifloon is one of the darkest Pokemon out there, and it's established that it can sometimes kidnap children, and make them disappear. Definitely not the usual wholesome Pokemon fare fans are used to.
Drifloon's Pokedex Entries are Terrifying
Drifloon was first introduced in Pokemon Diamond and Pearl, and its Pokedex entries were mostly tame at that point, but still set the stage.
Diamond - "A Pokémon formed by the spirits of people and Pokémon. It loves damp, humid seasons."
Pearl - "It tugs on the hands of children to steal them away. However, it gets pulled around instead."
HeartGold and SoulSilver are where things really start taking a turn, however, as it says children that mistake them for balloons oftentimes vanish. No explanation of if these children ever appear again, so presumably Drifloon is just kidnapping them. Then in Sun and Moon, the Pokedex entries really take a turn for the worse.
Sun - "Stories go that it grabs the hands of small children and drags them away to the afterlife. It dislikes heavy children."
Moon - "If for some reason its body bursts, its soul spills out with a screaming sound."
Ultra Moon expands on this by saying Drifloon's size increases each time it leads someone away. That's honestly terrifying and shows that Drifloon has a pension for kidnapping children and leading them to the afterlife, which is basically the same as killing them. More often than not, the cutest Pokemon turn out to be the ones with the darkest details. As another example, take Mimikyu, who's Pokedex entry reads, "Its actual appearance is unknown. A scholar who saw what was under its rag was overwhelmed by terror and died from the shock.
Things don't get any better with Drifloon's evolutions, as they still get up to the same hijinks, but their larger size means they can do it with anyone. Here's Drifblim's Pokedex entry from Shield, "It grabs people and Pokémon and carries them off somewhere. Where do they go? Nobody knows." Just remember their true nature next time before putting Drifloon on a Pokemon team.