PHILADELPHIA — Tina Fey’s “Mean Girls” can take credit for some of the most well-known movie quotes in the last 20 years of pop culture, from Gretchen Wieners’ catchphrase, “That’s so fetch,” to Karen Smith’s weather report, “There’s a 30 percent chance that it’s already raining.” In a recent interview promoting the Mean Girls musical movie (in theaters Jan. 12), Fey admitted that her favorite line uses the name of a real person she grew up with in Upper Darby: “You go, Glen Coco!” In the movie, Damien Leigh delivers the line as he hands out candy canes to high schoolers, prompting Wieners to …