The clip of thirteen year old Sophie on Valentine's day is actually a clip from Lizzie Mcguire, a show which Hillary Duff starred on as a teenager.
The side of the Little Caesar's pizza box says "Great pizza? Yep, in our playbook!" This is a potential reference to Barney's playbook that he used to pick up women.
The blue French horn and "have you met..." from HIMYM are both referenced.