Publicist Stephen Huvane told The New York Daily News his client had moisturizer applied to her legs by a makeup artist shortly before her "Tonight Show" appearance, causing the actress's legs to appear unusually shiny.
"It was clearly not quite absorbed in completely," Huvane told the newspaper in an e-mail.
The Daily News said O'Brien, who recently took over the "Tonight Show" from fellow comedian Jay Leno, did not use the result of the skin care product to poke fun at Paltrow.
Instead, the host of the NBC TV show asked the actress about her shiny gold dress, which he deemed distracting.
"I've been doing 'Iron Man,' so I thought it was appropriate," Paltrow said in response, referring to her role in the 2008 film and its upcoming sequel, "Iron Man 2."