The 60-year-old actor was recently approached by a man in Paris who thought he was the 51-year-old U2 singer, but it only happens when people have taken "a lot of medication" or are "completely s**tfaced".
Speaking at the UK launch of Warner Bros` animated movie `Happy Feet 2`, he joked to BANG Showbiz: "I had a guy come up to me in Paris saying, `Are you Bono?` Then he said, `Oh no, you`re not, you`re Robert Windsor`.
"I only really get mistaken for Bono by people who are really hammered. They have to be completely s**tfaced to think I`m Bono. I suppose when I put on the glasses I look a bit like him. It`s usually from a distance and by people who`ve had a lot of medication."
Despite being mistaken for the Irish star, the `Mrs. Doubtfire` actor - who is well known for being able to master a number of different accents and impressions - is unable to pull off an Irish accent to meet his high standards.
He added: "The Irish accent is one I just can`t seem to get. I always start doing it and then it just f**king fades. It always ends up going into Scottish."
`Happy Feet 2` is released on December 2 in the UK.