When Erica is pleading with Adam in his room, she suggests that she and her boyfriend should win "raddest couple" rather than "cutest couple" (listen closely and you can hear it clearly).
The cell phone Barry is holding in the beginning when in a suit is a model from the 1990s.
As Bev is pushing Marvin in the DeLorean, there's a sound of the engine being started even though his hands are on the steering wheel.