I wrote The Popularity Rules first, so when it came time to have Tasha's professor at Oxford, I realised that of course it would be Kat's mom! All my books take place in the same universe in my mind, so it made sense to have that follow through on the page. You'll also spot some people in PopRules talking about the reality show 5th Avenue, and Tasha's hot-tub scandal, and characters in all my books reference the same pop culture and celebrities: Chris Carmel, Lily Larton, the Alarm, Devon Darsel... It's easier to have fake pop culture, rather than risk celebs doing something to date the reference (see also, the cringeworthy reference to Chris Brown being dreamy in the 1st hardback editions of Sophomore Switch, shudder), plus, I think it's fun to have in-jokes like that for you readers to spot!