Album artwork in Erin's apartment on the wall in the last scene as she enters is from the soundtrack of One Tree Hill, which Sophia Bush starred in.
Nick Gehlfuss, Laura Wiggins, and Stephanie Fantauzzi all appeared on Shameless at some point. Gehlfuss as Robbie (Season 4), Wiggins as Karen (Seasons 1-3), and Fantauzzi as Estefania (Seasons 2-3).