How to Write Willow Speak
Getting Willow to sound like … Willow can sometimes be a challenge. Her way of speaking is very unique and by overusing any one specific characteristic of it can throw off your entire character. Below are a few suggestions that I’ve come up with to help the new (and experienced) Willow author perfect their Willow-speak.
1) Don't overuse the Willow-babble. She babbles sometimes, but not nearly as often as many people have her do in fics. And she usually does it when she's nervous, but again, if she's nervous a lot in your fic, then cut the babble waaaay back. Use it sparingly.
2) She isn't always straight-forward and she uses 'cute' words -- she often adds 'age' to the end of things to make new words. Slayage, snackage, etc. The same thing for adding -y to the end. "That sounds nice and girlfriend-y," Willow said, smiling happily.
3) Even when she's glum or depressed, she still sounds chipper. Overall (ignoring her descent into the dark), she's an optimist, always trying to find the bright side of things, even when she doesn't actually succeed. (i.e.- "It could be worse. We could all be sucked through a portal to Hell. Though really, the whole demons-migrate-to-Sunnydale thing isn't so fun either," she noted after a moment of thought.)
4) She's smart. She's a geek. She likes technical things, chemistry and math. She knows history, as well as pop culture. Throw in a geek reference, or something that has to do with modern-day teenage culture, would fit nicely. Keep in mind though that she wouldn't know Prada shoes from Payless, even in the later seasons. However, that's more because she didn't care than because her mother still picked out her clothing for her. She would get excited over the chemical properties of the mysterious green fungi that ... well, you get the picture.
5) She's a teenager. She says 'cool' and 'awesome' and 'oooh yay'. But she’s not a surfer or a Valley girl– Willow wouldn’t say ‘dude’, ‘rock on’, or ‘like, totally!’ See #4.
6) She's never, canonically, said 'Oh my goddess'. She has said 'oh my god.' She's not really wiccan so that makes sense ... but that's another essay. ;)
7) She doesn't curse too much. The “lunchtime be damned!” quote from Season One is particularly memorable, but other than that, she’s pretty calm in the cursing department. And if she does, she might make up curse words -- 'fiddlesticks' etc. It'd fit with her 'good girl' image growing up, and would be something Xander would tease her about I'd bet.
8) She does get mad, but she does it Willow-style. When it gets to a certain point, she tends to really go off (I’m thinking more yelling at Angel for not going on a date with Buffy and less Darth Rosenberg). It’s similar to Willow-babble, but has more finger-shaking and near-cursing. When she eventually looses steam, however, she kind of trails off, even in later seasons, from embarrassment.
Of course, there are many other characteristics inherent to Willow-speak, but these are the most prominent. If you’re unsure if you’ve got something correct, I encourage you to get a beta reader to look it over for you. He or she can give you suggestions on what to add, remove, or change to get your Willow to sound like Alyson Hannigan’s Willow. Good luck!