The actor plays school bully Draco Malfoy in the franchise and said that one overzealous fan changed his name to match his on-screen father's and wanted them to be a family.
He told GQ magazine, 'One guy wanted to adopt me.
'He'd legally changed his name to Lucius Malfoy and wanted to be a happy family. He didn't get a reply...'
The 21-year-old added that he is great friends with the film's star, Daniel Radcliffe and joked about a fake picture that appeared to show the two of them in bed.
'I saw this crude picture - all I'll say is that Daniel and I were never in that bed. Shame on whoever did that on Photoshop, it's caused me hell,' he said. 'My brother has it on his phone as a screensaver.'