Who is Gizmoduck?! is the twentieth episode of Ducktales's first season.
Donald Duck and Huey Duck are at the First National Bank trying to get a loan. Fenton Crackshell-Cabrera is there too, trying to open an account on his way to work (in spite of not having any money). The Beagle Boys arrive to rob the bank and Big Time Beagle threatens Huey. Fenton says, 'Blathering blatherskite!' and accidentally becomes Gizmoduck. He saves Huey, but he overloads the Gizmosuit's processor. It attempts to self-destruct, but Fenton cancels the self-destruction. Unfortunately, by that point he had already set the bank on fire.
Shortly afterward, Roxanne Featherly interviewed Huey on television. She paints Gizmoduck as being incompetent at best and evil at worst. Huey protests that Gizmoduck is a hero.
Watching the interview at home while trying to get a dent out of the Gizmosuit, the word "hero" resonates with Fenton. His mother, Officer Cabrera, then comes home from the police investigation of the bank. She tries to persuade her son to get a paid job (his intern job is for free). Throughout the conversation, the Gizmosuit goes off by mistake, necessitating Fenton hiding the damage before his M'ma notices. After they finish talking, Officer Cabrera tunes onto a telenovela, Patos de la Pasión.
At work, Gyro Gearloose reminds Fenton that he's allowed to use the Gizmosuit for nothing but basic tests. He notices the dent on the Gizmosuit, but Fenton takes his lunch break before Gyro can ask any questions. Gyro leaves to try to get a can of Pep out of the Money Bin's vending machine. There he meets Huey, who, not aware that Gyro didn't hear about the bank heist, talks to Gyro about the superhero he built for Duckburg. Gyro puts two and two together, and is not best pleased.
Meanwhile, Fenton is secretly testing the Gizmosuit's abilities at a construction site. He overloads the processor again, launching a rocket at Mark Beaks's helicopter. He tries to stop it, but fails to deflect the rocket from its course. He evacuates Beaks from the helicopter. Beaks then offers Gizmoduck a job, promising Gizmoduck that accepting the job will help him to help all of Duckburg. Fenton declines out of loyalty to Gyro. As he flies off, his battery runs out, causing him to crash.
Fenton wakes up in Gearloose Labs. Gyro immediately tells him he's fired. As Fenton is on his way out, he overhears Gyro telling Manny to incinerate the Gizmosuit. Pushed to the brink by this, Fenton activates the Gizmosuit and flies off to Waddle to accept Mark Beaks's offer. Mark Beaks attaches a device to the Gizmosuit and rebrands him "Waddleduck".
Fenton shows up for work at Waddle the next morning. Mark Beaks explains to Fenton that the device picks up help requests from users of the Waddle app. Fenton asks about helping people who haven't got the app or saving Duckburg from larger threats, but Beaks says that if he tries the device will override him. Furious, Fenton goes to work. All the jobs he's being called for are menial and unimportant. After first being forced to just helplessly watch the Beagle Boys mugging a family and then finding out that Huey has lost faith in him, Fenton tells Mark Beaks that he quits. Beaks then uses the device to steal the Gizmosuit. Beaks's security guards drag Fenton from Beaks's office while Fenton tries to warn Beaks about overloading the processor.
Beaks announces himself to the public as "Waddleduck 2.0". Huey points out that he's obviously not Gizmoduck, since not only did Gizmoduck save Beaks once, but Gizmoduck and Beaks have completely different faces. Beaks begins to play around with the Gizmosuit's gizmos, overloading the processor. Fenton tells him to cancel the self-destruction before it's too late, but Beaks is too panicked to think clearly. Beaks accidentally runs over his phone causing the device to fall off the Gizmosuit. Fenton summons the Gizmosuit back to himself to save his M'ma and Huey from Beaks's destruction. The processor is still overloaded, so Huey removes it and reroutes the Gizmosuit to use Fenton's brain instead. In addition to solving the fact that the original processor couldn't handle many gizmos at once, it also gives Fenton even more control over the Gizmosuit than he had before Beaks commandeered it. The original processor was still about to self-destruct, so Gizmoduck flew away from Duckburg with it. When it exploded, everyone presumed he was dead. While everyone mourns Gizmoduck's sacrifice, a very beat-up Fenton pulls himself out of the bay and passes out.
Fenton wakes up in the hospital, his worried mother at his bedside. She tells him that Scrooge McDuck paid for him to have the VIP hospital room. Scrooge himself shows up with Gyro; Officer Cabrera leaves so they can talk. Scrooge explains that since he travels so much, he can't always be there for Duckburg. He offers Gizmoduck a paid job protecting Duckburg on his behalf and Fenton gladly accepts.
- David Tennant as Scrooge McDuck
- Lin-Manuel Miranda as Fenton Crackshell-Cabrera/Gizmoduck
- Danny Pudi as Huey Duck
- Bobby Moynihan as Louie Duck
- Tony Anselmo as Donald Duck
- Jim Rash as Gyro Gearloose, Gizmosuit Bulby
- Selenis Leyva as Officer Cabrera
- Josh Brener as Mark Beaks
- Eric Bauza as the Beagle Boys
- Kari Wahlgren as Roxanne Featherly, Bank Manager, Intercom
- Keith Ferguson as Diego, Twin #1, News Announcer
- Jennifer Hale as Duck Mom
Names in Foreign Dubs
- Latin Spanish: ¿Quién es Pato Aparato? (Translation: Who is Device Duck?)
- Brazilian Portuguese: Quem é o Robopato?! (Translation: Who is Roboduck?!)
- The bank the episode opens in is named the First National Bank as a reference to Lin-Manuel Miranda's role as Alexander Hamilton.
- The sequence of Beaks donning the Gizmosuit is a parody of the transformation sequences from Sailor Moon.
- Donald attempts to get a loan to fix the damage his houseboat received during JAW$!
- Who is Gizmoduck?! was written twentieth, but aired eighteenth.