Penny is Jewish.
Penny has pretended to be Jewish on J-Date, taken up an Israeli martial art, and even created a Jewish alternate persona. Obviously her parents were Jewish, but converted when she was very young and kept this secret from her. She subconsciously remembers her Jewish childhood and this influences how she behaves.
Happy endings is Friends in an alternate universe
In this universe Monica and Ross aren't siblings, they are husband and wife, Joey had many women until he came out as a gay man with Rachel as the last girlfriend he had, Phoebe is Monica dumb blonde sister who dated Chandler for many years until the events of the first episode.
- Alternatively, and based on the character comparisons Brad makes while high on nitrous oxide, it's a world in which Monica and Rachel are sisters, Rachel left Ross at the altar, Joey was a gay man who failed at acting and went on a reality show instead, Phoebe was Monica's childhood friend who dated Joey while he was closeted, and Monica got married to Chandler much earlier after meeting him at that reality show while supporting Joey.
Happy Endings takes place in the same universe as It's Always Sunny In Philadelphia
Regan Burns appears as the manager of a pool club in the episode "Mac and Charlie: White Trash" during season season 6 of Always Sunny. He then appears in season 3 of Happy Endings as the manager of a private tennis club Brad and Jane are trying to join. Either the company who owns the tennis club in Chicago also owns the private pool in Philadelphia and he got transferred or he simply jumped on a great job opportunity in a not so far away city some time between 2010 and 2013.
Brooke, Jane and Alex are an interim version of the Charmed Ones.
The three of them never hang out long enough for their charmed status to activate, but in this case they're still witches individually.
Which explains Jane's seeming teleportation/transmogrification in Sabado-Free-Gante, and Alex's ability to continue to run a successful store with hardly any customers/win people over (power of persuasion?).
Also perhaps their family denied them their full powers due to the events of The Incident.
And Jane became more like the eldest sister in Brooke's absence as she says in Brothas & Sisters. Like how Piper took on the oldest sister role after Prue died.