Early Installment Weirdness: She's actually referred to as Kristin by Cheerleader in episode 1 ("Kristin, you look burnt. Or dead."). It's invoked, as What's Her Face later says "I miss Kristin-a".
Extracurricular Enthusiast: So and So explains that the "Priggity Prizom" is the name of this year's prom, and adds, with a deranged look, "I was on every committee ever." This fits well with the preppy overachiever stereotype she personifies.
Grammar Nazi: She's very annoyed with the other girls referring to Valentine's Day as "Valentimes". Like everything else in this strip, it gets her killed.
Hollywood Nerd: Despite being bookish, she's still into her looks. How attractive she is is difficult to tell from the artwork, but she's not considered hideous like The Ugly One.
I Die Free: In Issue 12, she throws herself into the garbage disposal when the cops show up.
Adorkable: When talking to a group of boys, she introduces herself by saying "Uh... hi. I like music, and, um... cloth."
Catchphrase: "I think I have a chance with this guy." Often used whenever Thomas the alien shows up.
Deadpan Snarker: She's the one who makes the snarkiest observations about her friends' activities. She was voted Least Likely To Care in high school.
The Friend Nobody Likes: What's Her Face is explicitly called the "pity friend" and is the one the other three are most likely to ditch or relegate to least-desired roles.
Limited Wardrobe: When the girls go to the beach, her intro card is "Same clothes". Of course, she isn't actually invited to the beach.
Nobody Loves the Bassist: When the girls form a group called "Kissyboots", she asks if she can't get stuck playing bass. Of course, Cheerleader shoots this down and makes her play the bass, which turns into a shark and eats her.
Official Couple: With Sci-Fi Greg. They used to date until Cheerleader demanded What's Her Face break up with him, and they went to the Priggidy Prizom together (or rather, they would have if What's Her Face hadn't gotten sparrow'd beforehand).
Only Sane Woman: She's more grounded than the rest of the girls, though this doesn't make her less susceptible to hilariously violent deaths.
Ambiguous Gender: Her intro card for "Teeny Tiny Girl Squad" asks if she's a boy or a girl.
Cloudcuckoolander: Her grip on reality is tenuous at best. Her intro cards are full of non-sequiters and when she visits the beach, her swimming costume is a three piece. She also prefers to get paid in plain yogurt cups for babysitting.
Meganekko: She wears hilariously outdated glasses that look like they're from The 50s.
The Pig Pen: Her personal hygiene is suspect. When Cheerleader gets run over, she gleefully states that she can stop showering.
Refugee from TV Land: When Strong Bad's computer gets hit with a virus, she shows up and attacks the King Of Town.
She Cleans Up Nicely: At her Sweet Someteenth birthday party, she comes out dolled up to the point where Strong Bad has to do a double take, even retracting his "Arrowed 2: Electric Boogaloo" death he had planned for her.
Spell My Name with a "The": Since her father's name is actually Manolios Ugly One, it's very possible that her first name is actually The. This isn't out of place in the Homestar Runner 'verse, as The Cheat, The Paper and The Stick are also referred to as such.
Unexplained Recovery: After she gets MSG'd in Issue 3, she appears in the dressing room with Cheerleader and So and So. She states that her stomach feels better.
Bald of Awesome: He's balding, but he's also responsible for many of the more hilarious deaths.
Comedic Sociopathy: He's responsible for many of the more hilarious and unusual deaths of the girls.
Universal Driver's License: He's seen driving a van, a boat and a brain mech, all of which result in the deaths of some of the girls.
Wicked Stepmother: If he is indeed Judith So-And-So-Erson, given that he kills the girls constantly.
The Napoleon: In his first appearance, his height is an issue for him. He gets angry at the girls for mocking him over it. When Tompkins says, "Heck, I'm taller than you," the girls promptly shout that he said a bad word. He immediately runs away and dies... somehow.
Narrator Strong Bad:(as if unsure on how to kill Tompkins off) AGGH! GRAGH! And... he died somehow.
Go Out with a Smile: Tompkins complains that he should have been killed as a prom date. Then, he gets riddled with arrows by a cardboard cutout of Tenerence Love. Notice that he has a huge grin on his face when this happens.
Promotion to Opening Titles: Inverted. His first appearance is in the opening titles of "Teeny Tiny Girl Squad", but he doesn't get on them in subsequent appearances.
The Slacker: He doesn't care much for anything but video games.
Defied with Sci-Fi Greg, at least based on his reaction to Chizuko. He states that one would expect him, a sci-fi geek, to be this trope. However, Chizuko is so far into the uncanny valley that she makes him sick to his stomach. In addition, Sci-Fi Greg's heart belongs to What's Her Face, anyway.