* Christina being unable to deal with Burke being shot makes a lot more sense after we learn that her father died in a car accident right in front of her when she was nine. However, she manages to overcome this, and [[spoiler: fares much better when Owen is shot]].
* Episode "If/Then" (the alternate universe episode) has a lot of them.
** Charlie [[spoiler:who had been previously shot]] says at one point [[spoiler:"Shoot me!"]]
** Bailey in braids: a call back to an earlier episode where she was shown as a meek intern known as Mandy wearing cornrow braids.
** Why would Kepner and Mer be friends? Mer hates her... oh, wait, Mer hates her because [[spoiler:Kepner had a crush on Mer's husband, Derek]] in the real world. In this alternate universe [[spoiler:Mer and Derek never got together, so Mer never hated Kepner for having a crush on her husband]].
** Callie thinks that Owen is Skyping with a MAN named Teddy. Hooray for ColorblindCasting and GenderNeutralWriting.
** The "I'm just a girl in a bar" dialogue between Meredith and Derek is the same conversation they had in their first meeting.
** The music has been used in previous episodes. "You Wouldn't Like Me If You Met Me" by Tegan and Sara was used in S1 E2; "Fools in Love" by Inara George was used in S2 E3; "Into the Fire" by Thirteen Senses was used in S1 E1; "Portions for Foxes" by Rilo Kiley was used in S1 E1; "Ruby Blue" by Roisin Murphy was used in S2 E3.
** Karev says "I always say never mess with the crazy chicks," which is ironic because he was involved with Rebecca [[spoiler:who went crazy and had to be committed]] and right after, he says "she's probably gonna go full-on Izzie," referring to the only other serious relationship he ever had on the show.
** Cristina and Meredith have the "We don't have to do the thing where..." dialogue previously used in a few episodes, originating in S1 E1.
** Why would Karev date Meredith and act like a good guy despite his backstory ? Because he knows that Meredith is the chief's daughter and could get favor by taking her last name.

* "You have apple hair. I threw a pancake in the river! The River!" It seems funny at first. Until it's not.