The girls George mentions in panel three are: Mel from d20 Monkey, Buffy (John & George's neighbor who's currently involved with Drew), Isabel from Woody After Hours, Valerie the hippie and of course, Glenda.

The bit about Mel from d20 Monkey comes from a conversation that Brian and I had that would have both of our comics in a shared universe... like how Woody After Hours and the characters therein are also in same world as Zombie Roomie.

Mel and John would have dated before Zombie Roomie started and she moved to wherever d20 Monkey takes place and sometime after she joined Sam's D&D game. Here's John's appearance from Mel's point of view.

https://d20monkey.com/comic/the-answer/