Howard makes a point of how everyone's tired of him bragging about being in space by doing a perfect imitation of Bernadette, to which she responds (in a lower tone than usual) "I don't sound like that." Melissa Rauch uses her actual voice when saying this line.
When Amy and Sheldon are trying to figure out their couple costume, one suggestion on Amy's side is Blossom and Joey. Mayim Bialik played Blossom on the TV series Blossom (1990).
Buzz Aldrin, the second man to walk on the moon after Neil Armstrong, makes his first guest appearance on the show.
Besides the above mentioned couples costume ideas, the ones listed on Sheldon's side are R2-D2 and C-3PO, Hewlett & Packard, Batman & Robin, Jobs & Wozniak, Kirk & Spock, Arthur Dent & Ford Prefect, and Doctor Who & a Dalek. The ones on Amy's side (besides those mentioned above), are Cinderella & Prince Charming, Anthony & Cleopatra, Lady & Tramp, Romeo & Juliet, Jack & Rose from Titanic (1997), and Dharma & Greg (a show also produced by Chuck Lorre). Also mentioned in dialog: Sheldon suggests salt and pepper (the condiments, not the rappers), and Amy offers Raggedy Ann and Andy.
Leonard and Penny's tryst inside the TARDIS is an inside joke. It parodies the honeymoon of the Doctor's companions Amy Pond and Rory Williams in Doctor Who (2005), which took place inside the TARDIS and is a major plot point of the sixth season. In addition, Penny wears a sexy Policewoman's outfit, parodying Amy's job as a kiss-o-gram girl in a similar costume.