Holly Marie Combs and Alyssa Milano play Heidi and Haylee Peterson, respectively. They previously played sisters in the original Charmed (1998) who also shared names with the same first letter, Piper and Phoebe Haliwell. Their initials are reversed. Further, one of the main themes in Charmed was "the power of three" since there were three sisters, just as in their characters on Grey's.
When DeLuca is dropping Meredith off at the beginning of this episode Meredith is wearing a baseball cap from the Seattle Grace-Mercy West baseball team she was on in season 8.
This episode's title is taken from a 1978 song by Peaches & Herb.