Franke and Kitty from Psychonauts

Franke and Kitty are two preteen characters in Psychonauts who are best friends. I haven't played the game since 2008 but I'm pretty sure they spend the entire game hanging out and doing nails together.

The official site parodying Friendster, Campster, has articles on both. [Kitty] (http://www.doublefine.com/campster/Kitty.htm)'s outright says she's in an "open relationship" and she's interested in both men and women (plus her favorite show is Xena). [Franke] (http://www.doublefine.com/campster/Franke.htm) is also in an "open marriage", likes TATU, Ellen, Laverne & Shirley, The Hunger (1983)...

I don't think it's stated they're dating one another, but it seems fairly obvious.

I wouldn't have known they were a couple by the game itself.