Bebe had only just signed for Vitoria de Guimaraes when he opted to make the £7.4m move to Old Trafford, but the Portuguese attacker has admitted that he never took his time at the club seriously.
The 22-year-old told Maisfutebol: "It was all very sudden and unexpected. I was on the train and the club called me. He said I must go and see my agent, and when I arrived, he asked if I wanted to go to Manchester United.
"I didn't believe him. I thought he was joking. I never took Manchester United seriously."
Bebe has spent the season on loan at Rio Ave after failing to start a Premier League match for Manchester United.