First recorded by Johnny Duncan (1960).
Hit version by Rick Nelson (US #9/UK #2 1961).
From the wiki: “‘Hello Mary Lou’ was written by Gene Pitney (‘Pretty Flamingo‘) and Father Cayet Mangiaracina, first performed and recorded by Johnny Duncan in 1960, and later recorded by Rick Nelson in 1961. Duncan’s recording took place at Norman Petty Studio, in Clovis, NM – where Buddy Holly, Roy Orbison, Buddy Knox, Waylon Jennings and others had also recorded – with Petty producing.
“Nelson’s recording features an influential guitar solo by James Burton (who is often cited as an influence by later guitarists such as Queen’s Brian May), and appeared on the Rick is 21 album (1961) – the first album to credit his first name as ‘Rick’; previous albums were credited to ‘Ricky Nelson’ … as was the promotional single.”