Perry told BBC's Newsbeat that her fiancé Russell Brand had an impact on Teenage Dream. Some of the tracks were recorded before the singer met the British comedian, but their relationship impacted on several of the later tracks. She said: "There are some songs on the album inspired by love. There's a song called Hummingbird Heartbeat. He gives me that Hummingbird Heartbeat."
With the exception of insects, hummingbirds while in flight have the highest metabolism of all animals. Their heart rate can reach as high as 1,260 beats per minute.
"The Night Chicago Died" was written and recorded by the British group Paper Lace. They talk about Al Capone in the song, but got a lot of details wrong - understandable since they wrote it based on gangster movies.
Phil Oakey recorded his vocals for "Don't You Want Me" in the studio bathroom. The recording was disrupted by guitarist Jo Callis reaching through an open window from outside to repeatedly flush one of the toilets.