- Alternative Character Interpretation: Superman gives up his powers when he is forced to kill Mr. Mxyzptlk. This is either his noblest act... or his most selfish. See the Analysis page for why.
- Anti-Climax Boss: The story seems to be building towards a major confrontation between Superman and Brainiac, but Brainiac is ultimately defeated by Lana, whose Mercy Kill of Lex robbed Brainiac of a viable host. Instead of a great battle, Brainiac simply breaks down at Supermans feet. Superman's true greatest threat is evil!Mxyzptlk.
- Lex himself, despite being Supermans most persistent and well known foe, is little more than a host for Brainiacs consciousness for the entire story.
- Complete Monster: Brainiac. He brainjacks Luthor in the most horrifying way possible, orchestrates the siege of the Fortress of Solitude, murders Jimmy Olsen, one of Superman's dearest remaining friends, and is completely devoid of anything resembling a conscience.
- Continuity Lockout: Shades of this, since it references Superman's history, both famed and obscure. However, that's the entire point of the two-parter, to briefly touch on the Superman mythos. Do you really have to have read the Jimmy Olson book in which he became Elastic Lad to enjoy the story?
- Evil Is Cool: Despite appearing in a few panels, Moore's revision of Mr. Mxyzptlk, has remained an iconic rendition of that character. Post-Crisis authors increasingly nerf him because Moore demonstrated quite successfully that the Fifth-Dimensional being is capable of being Superman's worst enemy.
- Gateway Series: Among modern readers, this is probably the Silver Age Superman people most often read even if it's the last.
- Harsher in Hindsight: The Prankster and Toyman were re-imagined as psychopaths in the Post-Crisis universe, making their decision to get back at Superman by murdering Pete Ross and outing Superman's secret identity more disturbing in retrospect.
- Heartwarming in Hindsight: Superman and Lois being parents to a son named Jon in the final scene eventually happened in the main canon thanks to DC Rebirth.
- Hilarious in Hindsight:
- One-Scene Wonder: Mr. Mxyzptlk appears in one-scene, and less than ten panels, but to say he steals the scene is an understatement.
- Batman and Robin attacking Brainiac's energy shield with sticks.
- Vartox's mere presence, for some, due to his... unique choice of clothes in the middle of a tense, tragic drama.
- After Brainiac attempts to continue the battle by taking control of Luthor's corpse, in one panel it looks like Luthor is making a derp face.
- Planet reporter Tim Crane's car looks like a Batmobile reject, and he himself is dressed like he's going to Studio 54 on the Planet Mongo. And what's with that face he has when Lois opens the door?
- They Wasted a Perfectly Good Character: Lex Luthor, Superman's greatest Arch-Enemy, the greatest criminal mind of our time, is reduced to a meat puppet in his final (Silver Age) appearance. THAT'S how Lex Luthor goes out. Moore does treat him respectfully by noting that Superman considers him and Brainiac his two greatest threats, but Brainiac is shown as Eviler Than Thou and then Evil!Mxy comes in and steals the show.
YMMV / Whatever Happened to the Man of Tomorrow?