Initially fearing that "Waterloo" might be too risky to enter for the 1974 Eurovision Song Contest, the group considered performing the ballad "Hasta Mañana" instead, as they thought that it was more in style with previous Eurovision winners.

Eventually, they decided on "Waterloo", primarily because it featured Agnetha Fältskog and Anni-Frid Lyngstad sharing lead vocals, whereas "Hasta Mañana" had Fältskog as the sole lead vocalist.

[citation needed] The song was still known under its original working title "Who's Gonna Love You?"

[1] The lyrics were later written by Stig Anderson while on a Christmas holiday to the Canary Islands and dictated over the telephone.

[2][1] In Australia, "Hasta Mañana" was used as a B-side on the "So Long" single (which never charted).