Waddle Doo did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Waddle Doo appears in Super Smash Bros. World Domination and is a cheatable character. It is a character who profiles beams and that is its profile. Waddle Doo is a minion of King Dedede and works with Waddle Dee, with lighning powers he can paralyse all of his opponents with quick dash attacks to finish the job.
He is a protector of Captain Waddle Deo and is thrown off the ship, Halberd at the beginning of the area. He appears at the end of the game at Waddle Dee's service with a broken arm from the fall of the Halberd.
If you use a Kirby amiibo whilst playing you unlock Mt.Dedede, Waddle Dees appear as enemies.
Kirby RPG and the Infinity Shard
Kirby RPG and the Infinity Shard includes Waddle Doos as enemies, they give Kirby the Beam ability. They are minions of Waddle Doodle, and will not attack Blaze, but will attack Kirby. Waddle Doos appear as enemies while Waddle Dees don't appear as enemies, but do appear as friendly NPCs.