The album marked the first conscious effort by John Linnell and John Flansburgh to branch out of their early sound, opting for more traditional rock rhythms and fuller arrangements. The duo adopted a backing band with live drums during the supporting tour. It was their last album recorded as a duo, and the band expanded to include a regular rhythm guitarist, bass player, and saxophone player for their subsequent releases. Apollo 18 also includes the "Fingertips" suite, a series of twenty-one short songs, most under thirty seconds long. The album generated three singles, "The Statue Got Me High", "The Guitar (The Lion Sleeps Tonight)" and "I Palindrome I", although only the first charted.
The album received mostly positive reviews from music critics, with many commending the band for making music with a darker tone. However, the album was criticized for lacking a stand-out lead single. Commercially, the album was not as successful as Flood (1990), peaking at number 99 on the Billboard 200 and spending only six weeks on that chart. In addition, some fans were upset that Flansburgh and Linnell opted to use a backing band for the album's tour, with some even boycotting shows.
— John Flansburgh on self-producing the album
After the major success of Flood (1990), Elektra sought out Elvis Costello to produce Apollo 18; however, John Linnell and John Flansburgh elected to produce the album themselves as they had originally planned. Prior to recording, the band upgraded many of their instruments; Flansburgh purchased a Marshall amp and Linnell bought several new saxophones. The album was recorded at The Magic Shop in New York City, in approximately ten weeks. Although the band recorded Apollo 18 primarily as a duo, its production is musically sparser than previous releases. This is reflected in the fact that the album's associated tour, the Don't Tread on the Cut-Up Snake World Tour 1992, was the band's first to utilize a live backing band, rather than a tape deck playing backing tracks. Linnell later noted that this led to much more complicated and deliberate rehearsals.
The music found on Apollo 18 is slightly darker in tone and mood than the songs found on Flood. When it came to writing songs for the album, Linnell and Flansburgh used "old standbys", such as producing harmonies through improvisation and generating melodies by sampling sounds in varying cycles. According to the album's press-release, however, Flansburgh and Linnell both sought to expand their horizons and incorporate new sounds and "extreme song arrangements".