C sharp, the sixth of E major, is a crucial pitch in this song. It's heard as the first note in the melody over the first two chords in both the verse and the chorus. Note that it's an appoggiatura (non-chordal tone) over both chords in the verse, though.
The chorus is almost the same exact melody, so what distinguishes it as more of a hook than the melody in the verse? There's the appearance of the title words, of course, but it's also significant that C sharp is not an appoggiatura over the vi chord in the second measure.
Finally getting that chordal tone as the first pitch over C sharp minor is more direct and grounds the song in its harmony. The grounding is emphasized by the fact it's also a longer pitch (a quarter note, as opposed to the eighth note in the verse) occurring on the strong downbeat.
*Note: Song written by Del Shannon and it also appears on his 1965 album 1,661 Seconds with Del Shannon.