Cincinnatus: In this—as in all incarnations of Superman—Clark has the power to amass great power and wealth if he chooses too, and could easily be the world's most feared villain due to his sheer power, but instead chooses to fight for Truth, Justice, and the American Way.
Corrupt the Cutie: Quite a few have attempted to do this; all have failed miserably and often end up on the receiving end of a hilarious put-down by Clark.
Good Is Not Dumb: As Superman, occasionally. Comes up with his more intelligent but vain foes who think Superman can be simply maneuvered around, such as those involved with Intergang. Occasionally, he runs into characters who think they take advantage of his honor as if it were naivete, but as Clark is quite quick witted he is easily able to Take a Third Option.
The Casanova: Has tons of women lusting after them—and he happily beds them—but he considers all of them trophies. The only one he actually wants for something more than a mere one night stand is a certain crusading reporter...
The Chessmaster: And he's frighteningly good at manipulating the entire population of Metropolis like pieces on a chessboard.
Graceful Loser: Of a sort. He has an uncanny ability to see the silver lining in defeat, and even when he can't he barely ever shows rage or pettiness or acts with anything but grace - perhaps because he believes that ultimately he will be victorious. For example, his reaction upon learning that an unstoppable virus is rampaging through is systems and may ruin him (and the world) is to have a cheerful discussion about philosophy and getting back to nature with his butler, and stays chipper even after he concludes that he would absolutely hate it. Whenever Superman beats him, he essentially shrugs, tips his hat and goes on to other schemes. But on the other hand, when all of his plans go horribly, horribly wrong, he has a quite more pronounced reaction.
Stalker with a Crush: Especially in his later appearances, where he's lost almost everything and Lois is much less interested in his advances.
Vague Age: He seems to be in his late 20s or early 30s, yet he somehow has children who are apparently middle-aged. It's possible he's Older Than He Looks.
Actually brought up by Clark in a Season 4 episode dealing with the aforementioned children. Lois questions how Lex could have kids so old, and Clark replies that Lex was such a Magnificent Bastard that his official age could very well be faked; thus the show seems to be implying that Lex is indeed Older Than He Looks.
Arch-Enemy: Considers himself one to Lois, and his plans always involve her in some way. Is also one of the few recurring villains not in some way connected to Intergang or Luthor.
Adaptational Badass: His comics counterpart is generally more of a nuisance, and certainly isn't anywhere near as dangerous as the career criminal mastermind he appears as here.
Bad Boss: Is incredibly abusive, both physically and verbally, towards his sidekick Victor.
Best Served Cold: He used to run a electronics company before Lois wrote an expose on his dirty dealing that put him in prison. Though he always has other, more important goals, humiliating and/or killing Lois always factor into his plans - sometimes to Revenge Before Reason levels.
Canon Foreigner: Sort of. The character of The Prankster is adapted from the comics, but his identity of Kyle Griffin is new.
Evil Has a Bad Sense of Humor: Despite his name, he's actually very humorless (though quite sardonic). Any actual jokes he makes tend to be either more of an act or incredibly mean spirited. He does, however, get a lot of genuine entertainment out of sadistically humiliating others - especially in his second appearance.
Gadgeteer Genius: Building weird but dangerous gadgets is his area of expertise.
Jerk Ass: In his own words, he never got time off in prison for good behavior because he's just not a very nice person. He's extremely nasty just for the sake of being nasty: this is a guy who tests out his freezing weapon on a woman with a baby standing under a falling piano, then decides to leave them there just for kicks.
Mad Scientist: In particular, he designs amazing weapons (to sell to various unsavory parties) and his assistant Victor builds them.
Manipulative Bastard: He takes the "distraction" theme of his comics counterpart turns it into his theme as a criminal mastermind. His entire schtick is using "pranks" to misdirect his enemies' attention, while he actually uses the confusion to accomplish hidden goals.