Fireflies

The single that would top charts around the world was never meant to be a single at all. "Fireflies" by Owl City was posted online as part of a single-a-month campaign, and manager Steve Bursky later admitted the song was not intended for release as a single. Adam Young himself felt it never "stood out" to him, but online popularity changed the plan, and Bursky called it an opportunity they couldn't pass up. When it featured as iTunes' free "Single of the Week," the track garnered 650,000 downloads, prompting Universal Republic to move the album Ocean Eyes' release date from September 1, 2009, to July 28.

Young wrote the song about insomnia, having first developed it awake in the early hours of the morning to occupy his mind. A camping trip to a remote lake in northern Minnesota also shaped it, as he tried to capture the experience of a meteor shower that suggested shooting stars being fireflies. Living with his parents, he recorded most of the track in their unfinished basement, layering dozens of instrumental parts including piano, organ, vibraphone, violin, viola, and cello, the last performed by a cellist he hired. Matt Thiessen contributed guest vocals, an artist Young had admired since high school.

The song reached number one on the Billboard Hot 100 during its tenth week, becoming Owl City's first chart-topper. In the United Kingdom, it made a 48-place jump from number 50 to number two, beaten only by Iyaz's "Replay," before topping the chart for three consecutive weeks. In March 2025, the single reached one billion streams on Spotify.