Waddle Dees have been in basically all Kirby games. They're best known as the dumbest and by far the easiest to defeat enemy. In games, all they've been known to do is walk or jump around. They occasionally get in Kirby's way, but their big eyes and cute little figures often portray them as innocent. In the games, there are tons of ways to defeat poor Waddle Dee. You can swallow him up (though he'll give you no ability), use any ability against him, or even release a puff of air on him.
Waddle Dee has a striking resemblance to Waddle Doo, which makes sense. They have a small and round figure, similar to Kirby. Also like the pink hero, they have big round feet. Waddle Dees have a red, orange and pink body with orange feet. They're eyes are big and black. In some games, they are holding a Parasol and floating down towards the bottom of the screen. This is the only time where if you swallow them, you'll get an ability: Parasol.
 In the Anime
It's unclear where these guys came from, But Waddle Dees are very far from evil in Kirby: Right Back at Ya! They stay in large groups in King Dedede's Castle, working and cleaning all day. There must be hundreds or even thousands of them, for without them the castle would surely be a pile of rubble. Waddle Dees cannot speak and communicate with the rest of the village. But they're translator Waddle Doo can, so there must be some type of language between them. Waddle Dees can be quite clumsy, falling on their faces a lot. But they listen to whatever their told to do and try their best, even though that may not be very great. It is assumed that Waddle Dees travel in groups, like nomads, until somebody offers them a place to stay. Though it probably wasn't Dedede himself, somebody let them in.
 Other Appearances
In Super Smash Bros Brawl, Waddle Dee appeared in King Dedede's final smash. They were as weak as they are in Kirby games though, and all they really do is walk around and annoy the opponents. But if you hit an opponent after you throw them, they do a decent amount of damage.