Along with the launch of Stray Kids' official website, JYP announced the release of the group's pre-debut extended play (EP) titled Mixtape. It contains seven tracks co-written and co-composed by the members, including "Hellevator" and other songs that they performed during the show. The EP, along with the performance video of its second track titled "Beware", was released on January 8, 2018, while the performance video of "Spread My Wings" was uploaded online a week later. It debuted at number 2 on Gaon's Album Chart and Billboard's World Albums chart.