You're not the Father is the 28th episode of Season 8, and the 318th episode overall. It revealed the Koopalings' pasts.
The Koopalings discover that Bowser Jr. is Bowser's only biological offspring. Bowser has no choice but tell the truth.
The Koopalings are fighting over the controller of their KoopaBox 720 yet again. Larry accidentally pushes the controller into a secret room that only Bowser and Kamek may enter. Despite Iggy's warnings, Larry jumps into the room, which apppears to be full of archives. Larry finds the controller near a document entitled "Profile - Bowser". When Larry reads it, the only name written at the "Children" header is Bowser Jr., much to his shock.
At the throne room, the seven Koopalings, the Mini Bowsers, Boom Boom and Pom Pom all confront Bowser. Bowser tries to run, but they all jump on him and pull him back. Bowser then explains the truth.
A few years ago, Bowser was feeling lonely at home. When taking a walk through Mushroom City, he notices an orphanage. Getting an idea (along with a light bulb appearing above his head, like in comic books), Bowser enters and asks if he can adopt children. The guy at the desk (reading a comic book and drinking soda and thus clearly not paying attention) says he's fine with it. After adopting seven children, Bowser erases their dark memories of the orphanage, as to make them have a very happy life.
Larry then asks how Bowser Jr. came around and where Jr.'s mother is. At this, Bowser grows quiet and refuses to speak. The Koopalings are confused, so at midnight they visit the archives again to find out.
- The KoopaBox 720 is a parody on the Xbox series of home consoles, made by Microsoft.