Betty originally had Dumb Blonde and Clingy Jealous Girl tendencies. She was even something of delusional in her obsession with Archie and would make schemes akin to Wily Coyote. By the 70s she was written as the level-headed tomboy we associate her with.
Veronica was more aggressive and generally mean early on. She didn't get along with Betty either. Over the decades she was toned down from an Alpha Bitch to a Lovable Alpha Bitch and is best friends with Betty.
In the first volume of The Demon Mages, the Gorgon actress Ari spoke without any pronounced accents. Outside of the comics, she's known for her Southern Belle-type accent. Only in the second half of the second volume does it begin to show.
Seems to have occurred with many Disney characters over decades of comic book appearances. Some examples:
Mickey Mouse. In "Mr. Slicker and the Egg Robbers" (1930), Mickey seems to be losing Minnie Mouse to Smug Snake Mr. Slicker (Montmorency Rodent). He even overhears a conversation where Minnie silently lets Slicker believe Mickey is just her "little brother". Mickey's reaction? He concludes "She doesn't care for me anymore - what is there to live for! Without Minnie, I might as well end it all". ... "I can't get Minnie off my mind! I just can't go on without her!" ... "Without Minnie, all my dreams have become nightmares" ... "Goodbye, Minnie! Goodbye, cruel word!". Only after four failed suicide attempts does he snap out of it. This is the same Mickey who would make an art of ditching Minnie to attend to his next mystery investigation/reporting/adventuring around the world. Later stories have made a running joke of the Mouse couple hardly spending any time together.
Phantom Blot. In "Mickey Outwits the Phantom Blot" (1939), the Blot is a rather scary opponent who easily overcomes Mickey on several occasions. With only one weakness. In his words "My cursed soft heart! I never could bear to SEE anything die! I'm just too tender for such things". So he sets elaborate death traps instead, leaving them to take care of Mickey. Mickey typically escapes with minimal injuries. The Blot remains highly efficient in most of his incarnations. But the soft heart is mostly forgotten about and he takes a more direct approach. For example in "The Hooded Eagle" (1994), the Blot has no problem attacking Mickey with an axe. After taking elaborate efforts to lure him to an isolated location of the Arctic, indicating he was planning about it for some time.
The Phantom Blot was in his early appearances portrayed as a master thief, and was actually unmasked at the end of his first appearances. Later he went from a thief into a full-blown super villain, and the fact he even had a face under the hood was forgotten (in one comic in particular Mickey meets the Blot's brother, who for some reason is also wearing a hood, and comments that he finds it hard to think of the Blot as a regular person with a family, instead of some kind of supernatural monster). He's started appearing unmasked from time to time, and has gone back to stealing things instead of trying to take over the world or whatever (although he still has access to various high-tech devices, usually stolen prototypes, that he uses to commit crimes).
Speaking of Disney, Scrooge McDuck. In his earlier appearances as a Donald Duck supporting character, Scrooge was mostly an antagonistic or even villainous character — there was the infamous robber baron flashback in "Voodoo Hoodoo", and in "The Magic Hourglass" Scrooge sics a band of hired thugs on Donald and threatens to leave his nephews to die of thirst in the desert if they won't give up the McGuffin he's after (though he isn't quite hard-hearted enough to go through with it). When Scrooge became the star of his own spinoff series, Barks had to make him more sympathetic and he quickly evolved into the proud and avaricious yet still honorable tightwad that we know today.
In his "Life and Times" seriesDon Rosa tried to explain the "Voodoo Hoodoo" incident as a huge mistake that Scrooge made as a young man in a moment of hubris and spent the rest of his life regretting; but this doesn't really fit with the Barks story where the present-day Scrooge is shown laughing at the memory.
His DuckTales incarnation takes a step even further, to the point of clashing with even the later comics version (and some early points of the show itself). While Scrooge remains somewhat curmudgeonly and closely tied to his money, he tames greatly, becoming more primarily a warm father figure for the triplets.
Gladstone Gander was only an arrogant dandy who served as The Rival for Donald in his first three appearances — him being Born Lucky on top of that wasn't established until his fourth appearance ("Race to the South Seas"), and even then this trait only existed intermittently for a while before becoming cemented as a permanent focus of his character.
Iznogoud: The Caliph's chamberlain introduced in Iznogoud's Birthday was initially not specifically aggressive to Iznogoud and starts acting antagonistic toward him as a reaction to his anger and obnoxiousness. When the same chamberlain is reintroduced in later comics, he is portrayed as being basically Iznogoud's Arch-Enemy who is trying to protect the Caliph against his overthrowing attempts. Being jailed at the end of Iznogoud's Birthday didn't help as well (although Iznogoud had good reasons to do that, to be fair).
In the original issues of Mandrake the Magician, Lothar was more or less Mandrake's negro manservant, never speaking, showing up whenever baggage needed to be carried or enemies needed to be beaten up, and vanishing between scenes when he wasn't needed. Once this became socially unacceptable, Lothar was rewritten as Mandrake's good friend, as well as a good deal smarter and proactive. On the other hand, Mandrake went from being a full-fledged wizard (kind of like a male Zatanna) to only being capable of using illusion magic.
Micronauts: Team leader Commander Arcturus Rann in the beginning had a more rakish personality somewhat like Han Solo. His speech included slang, mild swearing, and Solo-isms such as "Biotron, get your bolted butt back here!". Later, Rann's speech would become more mature and stilted as becoming of a legendary hero of the Microverse. On the other hand, Marionette, a princess of Homeworld, would start off speaking more formally, but later adopt hipster slang into her speech. Justified in her case as she is said to have spent some time on Earth away from the team.
The earlier far wackier points of series are rather jarring to see. Most notably the characterizations of Sonic and Robotnik are based more primarily on their Adventures of Sonic the Hedgehog counterparts, with Sonic being a goofy Karmic Trickster and Robotnik being a childish Harmless Villain. The other Freedom Fighters are far more comedic than they are in later issues and even the original show they came from. Princess Sally Acorn in particular started off as The Finicky One and was far more neurotic and self-righteous, before becoming Closer To Earth and much more lucid and easy going.
Snively was initially very loyal to Robotnik and wouldn't become The Starscream until The Death Egg Saga.
Amy is known as a badass Only Sane Man of the Freedom Fighters. Her earliest appearances, however, have her much like her game version would be known as. Amy is less proactive and teases Sonic a lot. This personality change was due to Executive Meddling, as it was thought female readers needed a strong female role model. She was mostly reversed in the final arc, the Adventure adaptation, which makes it seem odd when Amy is standing around instead of being in the action.
Robotnik was prone to horrible egg puns in early issues, which became downplayed as he shifted into the dictator figure.
Jaime from the Spanish Superlópez series was originally created as López's work rival, who would report everything he did wrong to their boss in an attempt to get him fired and take his girlfriend. They bonded notably in book no. 10 and became friends from then on, with Jaime appearing now as a nice, caring man. His old personality can only be seen briefly in Books 35 and 36.
The Splinter who is a loving, if flawed, father is nowhere in evidence in the first issue of Teenage Mutant Ninja Turtles, where he casually tells his sons that the reason he's been training them for years is so that they can attempt to kill a man they have never met to satisfy a vendetta they had never heard about before, a mission he intends for them to undertake with no actionable intelligence and no expectation of survival. While technically still canonical, future stories have had to gloss over these details, since they're completely at odds with the characters the turtles and Splinter would eventually become.
Tintin, in his earlier adventures, tended to defeat his enemies by beating them up. His condescension to the natives and cruelty to animals in Tintin in the Congo are a jarring contrast to his humane attitude in the later adventures.
Originally, the Tintin stories reflected the attitudes of Herge's mentors, who encouraged him to write religious and political propaganda pieces (Tintin in the Land of the Soviets) and his work reflected European colonial attitudes circa 1930. A turnaround came when Herge befriended a Chinese student in Brussels who taught him about Chinese society, politics, and culture. As a result The Blue Lotus is critical of Western imperialism in China and criticizes westerners making racist comments about the Chinese.
In the early "Man of Iron" story in the Marvel UK Transformers Generation 1 comic, Optimus Prime orders that the Man of Iron and his navigator and ship be destroyed to prevent the Decepticons getting their hands on them. This is the same Optimus Prime who generally goes out of his way to save noncombatants.
