The impromptu red carpet smooch by the two starlets Friday follows an interview in which Portman identified herself as "boring," the Daily Mail reported Saturday.
"The only thing that's a little bit annoying is that I feel that I come off kind of boring sometimes," the 26-year-old actress had told W magazine.
Johansson, 23, opposed Portman's "boring" stance during that interview, telling her "Boleyn Girl" co-star she didn't consider her boring.
"Boleyn Girl" is about two sisters, played by Johansson and Portman, who vie for the attention of Britain's King Henry VIII.
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