In the beginning, Circus had been planned as a re-release of Blackout. The re-release is said to have contained four bonus tracks, remixed versions of songs, and a DVD detailing the production of the album. However, these plans were later dropped and Circus became a full length album.
Many of the songs recorded for the album's original direction were not used for unknown reasons. This includes songs produced by Lil Jon, Akon, Sean Garrett, Pharrell, and additional songs by The Underdogs.
The title of the album was chosen prior to the album's completion.
"Mannequin" was supposed to be the fifth an final single off Circus, but was scrapped because Spears' label wanted to release The Singles Collection instead.
Some songs were written by Spears on piano ("My Baby").
"Out From Under" was supposed to be released as the third single, though "If U Seek Amy" was chosen instead.
Spears stated that the album title comes from the metaphor "for her life being a circus".
Danja's intro on "Kill The Lights" was taken from an actual news report from 1938.
"Unusual You" had a limited release in Australia and New Zealand, but was never actually released as a single.
The album was supposed to be released in early/mid-2009 but Jive rush released it in late 2008 instead; this is most likely because they wanted to quickly do some damage control on Spears's image after the disaster of the Blackout era.
In 2009, a Fantasy flanker fragrance was released, inspired by the album, and was titled Circus Fantasy. This makes Circus Spears' first (and to date, only) album to spawn a fragrance.
There was a speculation that The Circus Starring Britney Spears would have a DVD release in 2009. On November 12, 2009, Spears' manager, Adam Leber, posted on his Twitter account that there were "...No plans for a Circus Tour DVD at the moment."
On June 26, 2012, rumours arose on Perez Hilton's website stating that there was a DVD to be released after what appeared to be a trailer of unseen concert footage surfaced online. Despite this, no official DVD or recording has been released of the concert tour.
This is Britney Spears’ first album since Britney and Kevin: Chaotic to have a title track.
It was rumored that Spears wanted “Quicksand” on the standard edition of Circus, as Spears saw the song as a collaboration with Lady Gaga. The album's tracklisting had already gotten too long, however, and two of it's tracks ended up being removed from the tracklisting: “Phonography” and “Quicksand”.
Originally, Spears frowned upon the idea of "Radar" being released as a single. Unfortunately, due to a contract between the producers that stated at least one of the tracks that they had produced would become a single, it was included on Circus and released as a single (It is rumored that the original fourth single would’ve been “Out from Under” or "Mannequin").
Circus is also the first album Spears released during her 13 year conservatorship.
The Deluxe version of the album includes a DVD of the making of the album making it the first Britney album to include a DVD (excluding Britney DVDS which included exclusive CDS as they aren't considered albums).
