"Day of the Only Child!" is the sixteenth episode of the animated series DuckTales. It premiered on June 30, 2018. In it, Dewey invents a holiday that allows him and his brothers to be only children for a day, but they each realize that they need each other more than they thought.
Dewey schedules his self-invented "Only Child Day" for himself and his brothers. To Huey's dismay, it's on the same day of the Annual Junior Woodchucks 3-Man cook-out. Louie uses the holiday to socialize with Doofus Drake, the richest heir in Duckburg, despite Huey and Dewey's negative impressions towards Doofus.
Upset that his brothers won't partake in his activities, Huey attends the meeting nonetheless. But Launchpad, as troop leader, prohibits Huey from competing alone before Bouncer and Burger Beagle (disguised as scouts) offer to help. Despite their poor disguises, Launchpad falls for the ruse and assigns them with Huey. Still, the Beagle Boys' shoddy trap construction encourages Huey to teach them how to make better ones. Astonished by Huey's respect towards them, Bouncer and Burger eventually tie up to Big Time to a tree when he threatens Huey; Huey climbs to rescue Big Time, but the other Beagles make the situation worse when they blindly follow Huey's orders, and the tree crashes.
Louie goes to Doofus' residence and meets Doofus, although Doofus' quirky nature alienates Louie until Doofus offers Louie a bracelet to entice him as a "friend". When Doofus takes Louie to a treasure room, he carelessly begins breaking stuff and encourages Louie to do the same; however, Doofus suddenly becomes defensive towards a portrait of his late grandmother and throws a fit towards his servants, who turn out to be his parents. They reveal that the wealth Doofus inherited from his grandmother changed Doofus into an obsessive creature of habit. Doofus' parents warn Louie to escape, but he is trapped by Doofus' magnetized bracelet. Doofus proceeds to punish Louie until a tree crashes into the ceiling, dropping Huey and the Beagle Boys in.
At McDuck Manor, Dewey records a mock late-night talk show as an audition tape for himself. To act out interviewing, Dewey uses toys as exaggerated stand-ins for his brothers; but the dialogue attracts the mansion's new security drone interpreting it is an intruder, so it begins attacking. After the drone chastises Dewey, Dewey realizes that it's actually Webby inside the drone so she drops the act because she was worried the boys would break up. Unfortunately, the drone malfunctions and threatens them before Dewey climbs onto it and carries him off.
The drone lands Dewey at Doofus' home where Huey and Louie are. Reunited, the boys work together to defeat Doofus, reconcile the Beagles, and reprogram the drone to escape the mansion. Webby comes shortly after and the boys assuage her they are still brothers but do need time to be themselves. The kids walk home while Webby sings the theme to Dewey's show to Dewey's annoyance.
- Danny Pudi as Huey Duck
- Ben Schwartz as Dewey Duck
- Bobby Moynihan as Louie Duck
- Kate Micucci as Webby Vanderquack
- Beck Bennett as Launchpad McQuack
- John Gemberling as Doofus Drake
- Eric Bauza as the Beagle Boys
- Yuri Lowenthal as Doofus' Father, DT-87 Drone
- Tara Platt as Doofus' Mother
- The security drone's model number, DT-87, is both a reference to the original DuckTales and the same reference used in "McMystery at McDuck McManor!".
- Yuri Lowenthal and Tara Platt who voice Mr. and Mrs. Drake respectively, are married in real life.
- The drone is based on the ED-209 from the RoboCop franchise. The scene where the drone asks Dewey and Webby to comply and proceeds to shoot them anyway due to a malfunction despite complying with its demands is a reference to the ED-209 asking an OMNICORP employee to comply and proceeding to shoot him anyway due to a malfunction despite complying with its demands during a demonstration.
- This is the third episode of the series where Scrooge McDuck is absent. The other two were "The Beagle Birthday Massacre!" and "Terror of the Terra-firmians!".