The 32-year-old star appeared on the show as David Letterman celebrated his birthday.
Holmes read out the 'Reasons why I'm presenting the Top Ten List' on the show.
Her reasons were: number ten - 'Lost a bet with Tom', number nine - 'They told me this was 'Lopez Tonight', number eight - 'When I heard Bjorn Lomborg was going to be here, how could I say no?', number seven - 'This and an hour of traffic school gets me out of a speeding ticket' and number six - 'I'm here tonight anyway playing bass with the Foo Fighters'.
She then continued to read the list: number five - 'I was in the neighbourhood auditioning for Katie Couric's job', number four - 'It kills time before my table's ready at the Cheesecake Factory', number three - 'Honestly, I have no idea', number two - 'It's easier than getting Dave a birthday present' and number one was - 'What's the downside? No one's going to see this'.