Mr. Wonderful is a one-shot Darkwing Duck villain who appears in the two-part comic story "Super Union Blues" (published in Disney Adventures Volume 3, Numbers 6-7). He is a parody of Mr. Fantastic from Marvel Comics' Fantastic Four.
In the first half of the story, Mr. Wonderful is introduced as a delegate of the Super-Hero Union, which Gizmoduck is also a member of. He and Gizmoduck show up in St. Canard to award Darkwing Duck a membership in the Union. Darkwing, however, refuses to join the Super-Hero Union, and Mr. Wonderful arrogantly retorts that if he keeps working independently, he'll be undermining the Union. Thus, over the next several days, every time a crime occurs in St. Canard, Mr. Wonderful has his three teammates - Monkeyflash, Screaming Mimi, and Lenny - stop it before Darkwing can show up. Sure enough, this drives Darkwing into almost giving up on fighting crime himself, but Launchpad is able to snap him out of it.
As it turns out, though, Darkwing was completely right to distrust Mr. Wonderful, as Gizmoduck soon finds him having a video chat with Steelbeak, thus revealing that Mr. Wonderful is actually an agent of F.O.W.L. Gizmoduck zooms off to go warn Darkwing, but not before Mr. Wonderful calls for Monkeyflash, Mimi, and Lenny and tells them that they have to destroy Gizmoduck, claiming that he is actually an evil clone created from a speck of dandruff from the real Gizmoduck. When Mr. Wonderful and his three duped minions catch up with the heroes, he then claims to be joined by the leader of the Super-Hero Union, Ulti-Man, actually a disguised Steelbeak. However, Mr. Wonderful's charade comes to an end when the real Ulti-Man shows up to give him a subpoena for impersonating the Super-Hero Union.
As Steelbeak escapes in a helicopter, he informs Mr. Wonderful that he has officially been dropped several notches on his "reliable flunkies" list, and orders him to at least try and defeat Darkwing. In the fight that follows, Mr. Wonderful reveals his superpower - the ability to stretch his arms and legs like rubber. Darkwing remarks that he will now officially refer to Mr. Wonderful as "the Rubber Duckie" from now on and then gives him a face full of relaxative gas, causing him to fall down in defeat.