When Superman tells Supergirl that nature wins over nurture, Mr. Mxyzptlk tests it by giving them different places of origin, but will time-travelling Booster Gold be able to reverse the change?
A Daily Planet televised news program has two main stories for the audience but, although they are about familiar people, they do not present them in the expected way. The first tells (in the manner of "The March of Time" cinema news of World War Two) that the West has been invaded by the forces of the militaristic, Soviet-style Peoples Republic of Kasnia and are spear-headed by a super-powered character called "The Superman." Then the news moves on to entertainment and the second story tells us of Kara Zor-El, the star of the popular reality TV show "That's so Kara." It is confirmed that she is from Krypton, has super-powers and wears a Supergirl outfit but otherwise she only seems interested in her business ventures and her appearance. The news presenter speculates what the world could be like if these two super characters were to unite in the cause of justice but then dismisses the idea with a laugh.
At a movie premiere (or something similar), Kara steps out of a limousine onto the red carpet and basks in the attention of the fans, reporters and photographers. In the crowd, a young woman addresses her as Supergirl and asks for help. Kara only dimly recognises the name but feels that she ought to be helping people. Then it begins to be more obvious what is happening as out of the crowd steps her diminuitive and garrulous agent who is a lightly disguised version of the magical mischief-maker Mr. Mxyzptlk. He tells her to forget about helping people and focus on her adoring public. Kara agrees but the Kasnian Superman descends suddenly and smashes her limousine, plants the enemy flag and declares (in a Russian accent) that everything belongs to Kasnia. After he flies off, a livid Kara decides to go and tell the Superman to stay out of her way. Mxyzptlk, looking to cause mischief, eggs her on as she flies away.
The Kasnian Superman is in front of the Daily Planet offices which has been draped with a banner that hails the state of Kasnia. Supergirl appears and there follows an extended battle between the two in front of the building. In the middle of this, a space-time portal opens and out steps Booster Gold who just watches the fight continue. He notices Mr. Mxyzptlk standing nearby but does not recognise him. Striking up a conversation, he tells him that he has been away in his retreat beyond space-time (probably Vanishing Point) but on returning finds that Superman and Supergirl are dressed differently and are fighting one another and the Justice League no longer exist. He decides to stop the fight and gets between the antagonists with a force-field bubble. Speaking to the Kasnian Superman, he tells him that his opponent is his cousin and they are both from Krypton and Kansas.
The last name jogs the Superman's memory as he remembers being in Kansas on a previous occasion with Supergirl to deal with an outbreak of twisters. When they have dealt with them they head for the Kent Farm and eat some blueberry pie while they wonder if their lives would have been different if they had not come from Smallville. But, overhearing them is Mr. Mxyzptlk who speaks to them from a television showing a phoney program called "The Mxy Zone" (in the style of the old TV program The Twilight Zone.) He tells them he will test their belief that their origin place makes little difference by sending one of them to wartorn Kasnia and the other to shallow Hollywood.
The Kasnian Superman, at the Daily Planet building, begins to realise that Mxyzptlk has tricked them but still has to convince Kara. When Booster Gold reveals that Kara's agent is the imp by asking for a spot on The Mxy Zone, the Kasnian is finally convinced, and Mxyzptlk, changing from the agent, takes revenge by dropping the metal globe from the top of the Daily Planet offices onto Booster's head. When the imp tries to recontinue his mischief, the Kasnian says this will not happen giving a saying from his home country as his reason. Mr. Mxyzptlk can understand it except for the last word which he repeats back and it is, inevitably, his name backwards, causing him to vanish and the world to return to normal.
Restored to the Kent Farm, Superman and Supergirl can remember everything that happened and Superman tries to reassure that he would never do those things in normal life. Supergirl accepts this and confirms her familial love for him. Then Booster Gold shows that he has survived by appearing from inside the house but disappears again quickly to avoid having to explain where the blueberry pie has gone.
Appearing in "Keeping Up with the Kryptonians"
- The episode's title is a reference to the reality show Keeping Up with the Kardashians.
- "The Mxy Zone" is a reference to The Twilight Zone for Mr. Mxyzptlk is from the 5th Dimension, which is a dimension of imagination.