The exclamation of surprise in popular music is an often overlooked subject in musicology. But there exists a rich vein of declarations and exaltations since the very birth of rock'n'roll. Little Richard sang "Oh my soul", and Jerry Lee Lewis exclaimed "Goodness gracious!"
In the 70's pop lyricists bought the cry of amazement to new heights. Famously, the song "Bohemian Rhapsody" by Queen (containing the phrase "mama mia") was knocked off the number one spot by the Abba song "Mama mia" - the only time an exclamation of surprise has knocked itself off number on in all musical history! Furthermore in 1971 Marvin Gaye sang both "Mercy me" and "What's going on?" in the space of one album. Giddy times, indeed.
Since then, things have cooled off for surprise in songs. Not including the use of "hello" (qv, Lionel Ritchie), examples become a bit sparse. Ian Dury said "knock me down with a feather", before the Bee Gees took the exclamation back to number one, with "You Win Again", which includes a section where they beautifully harmonise around the saying "Well, I'll be!" Genius. Will we see it's like again? Only the future generations of songwriters can answer that one.