Best Friends Whenever season 1 episode 11
Episode title: Cyd and Shelby Strike Back (1)
When the girls discover inventor and GDD CEO Janet Smythe is behind the future lab, they decide to fight back and travel to the past to stop Janet from starting the corporation. Their plan seems to work until they realize they also stopped other major events from happening in their lives, including them living together and Barry and Marci falling for each other.
