the song "J.A.R." by Green Day, which has a distinctive intro on bass guitar. While practicing playing the riff, Hoppus came up with a new song derived from his failure to perform the part correctly. Though he initially developed it as a vulgar joke song, he felt it had potential as a regular tune. Hoppus claims it took him five minutes to write. He later presented the song to the band while rehearsing at DML Studios in Escondido, California, where they had booked time for two weeks to write new songs. Earlier that year, Raynor had been expelled from the group and replaced with percussionist Travis Barker, previously of the ska-punk act the Aquabats. He and DeLonge found the composition agreeable and further developed it in the rehearsal space. The story in the song is not strictly autobiographical, but its central theme resonated with Hoppus, who spent his twenties by his own admission "acting like a jackass teenager". Barker agreed, later commenting: "[Mark] was a grown man but kept acting like a kid." Many Blink songs center on maturity—"more specifically, their lack of it, their attitude toward their lack of it, or their eventual wide-eyed exploration of it" according to writer Nitsuh Abebe. Composition "What's My Age Again?" is credited to Tom DeLonge and Mark Hoppus. Though Barker helped write the songs on Enema of the State, only Hoppus and DeLonge received songwriting credits, as Barker was technically a hired musician, not official band member. The song is two minutes and twenty-eight seconds long. The song is composed in the key of G-flat major and is set in time signature of common time with a driving tempo of 158 beats per minute. Hoppus' vocal range spans from Db3 to Gb4. It follows a I–V–vi–IV chord progression, common across several genres of music. The band utilize the progression in numerous other singles; music educator and author Dan Bennett claims the progression is sometimes called the "pop-punk progression" because of its frequent use in the genre. The song is incredibly brief compared to most singles; within one minute, nearly two full verses and a chorus have been completed, and it in total runs two minutes and twenty-six seconds. The song opens with a catchy, arpeggiated guitar part, following the song's chords in playing the root of each chord. The part has been considered tricky to perform; given its quick, articulated nature, it