“Blank slate protagonists” are heroes who generally have no personality to speak of, and are generally meant to be little more than self-inserts for the audience. This trope is for those protagonists who start with having no personality… and when they finally get one, it’s the most chaotic persona possible.
1) Louie (Pikmin)
Louie is introduced as Olimar’s junior partner and trainee in Pikmin 2, and is designed with as little of a personality as possible. At most, Louie is initially depicted as a slacker employee of Hoctate Express. He is effectively a duplicate of Olimar (down to his name being a sendup to “Luigi”, Nintendo’s first player 2 character”, and much like any Player 2, has little personality to speak of.
However, the game subverts this. Louie not only is left behind in the middle of the game, he thrives on an alien planet by eating the local flora and fauna (down to suggesting cooking methods in his notes). While he’s considered little more than a foolish slacker, the game implies Louie actually likes his new life and is willing to kill others to keep it. The following games double down on this by not only making him something of a malignant recurring presence (being focused on his gluttony), but also make him a sociopath who regularly compromises missions with a pretty flagrant lack of care.
This ends with Louie both a hated and loved character in the franchise, and being rather infamous among Nintendo fans as one of Nintendo’s most unhinged characters
2) Prince Charming (Cinderella)
Disney’s Prince Charming is rather infamously bland, being little more than a perfect love interest for Cinderella to win over. This is mostly a hangup from Cinderella being THE Disney princess movie, and at its time of initial release, didn’t need much thought to round out his character.
Still, Charming has an overall negative reputation for his lack of personality. Cinderella III, a direct-to-video sequel, made an effort to fix this a little bit, and as a result, is largely known today for one particular scene.
That is to say, the scene where Charming throws himself out of an open window as a form of malicious compliance to his father. It’s a completely out-of-left-field characterization for him, but it’s largely preferred by fans, as it gives the prince a completely fun personality that matches Cinderella’s groundedness quite well. Plus, it’s absolutely hilarious watching Charming defenestrate himself.
3) Sgt. Cortez (Timesplitters: Future Perfect)
The Timesplitters games had exponentially more plot as the series progressed. The first game had an excuse plot to justify its random historical/genre scenarios. The second game introduced Sgt. Cortez as the protagonist of the “Timesplitter War”, but gave him little characterization beyond that of a generic space marine and action hero.
Timesplitters: Future Perfect completely changes this, and makes Cortez the main protagonist. Not only is he an invested badass, he’s also a dude with more than a few screws loose in every scenario he’s put in: he easily befriends an esoteric archeologist, a groovy 70’s super spy, a final girl in a horror movie, a cutthroat corporate ninja, a robot with a virus, and himself from different time periods. Cortez goes from “generic” action hero to a hero with a “tude”.
More to the point, the game also paints him as a bit of a dork. Cortez keeps practicing lame one-liners, has a corny catchphrase (that literally everybody feels awkward around every time he uses it), and regularly stumbles across the plot by sheer accident.
Still, Cortez’s wacky nature and tongue-in-cheek machismo do a lot to differentiate himself from the self-serious games from the time, and stand out to make Timesplitters a cult classic.