The presenter jokingly described Watson as "a bit of an animal" and the comments were later wrongly attributed to Radcliffe.
And the star admits Watson gave him a tough time when they later met up on the red carpet.
He tells Reuters, "When you're in this period of time when you do an interview and it's aired the next day, your quotes come back at you so quickly. On Daybreak the other day... Kate Garraway was interviewing me... and she said 'Oh the kiss with Emma in this film, she's a bit of an animal, isn't she?' and I said 'Yes', and then it was like I'd said it.
"Emma hit me on the arm as soon as we came off the red carpet (at the film premiere) and said 'What have you been saying to people about me?'."