Derren Brown made Simon Pegg forget the present he wanted and made him want something else. At the end he says he used hypnosis but this is what i believe he did.
You sat right there can easily perform this trick even if you have no hypnosis knowledge at all. Ask a spectator to write down a present that they want on a piece of paper fold it up and put it in their pocket. If you do not know how to pick pocket ask them to place it in their back pocket but if you do know how to pickpocket yo can let them put it in any pocket they wish but don't worry soon i will hopefully have a video out on how to pickpocket so you can learn from their.
Once they do that you replace their piece of paper in their pocket with your piece of paper which has another present on their. I will now give a quick explanation on how to pickpocket something from someones back pocket. Start walking around the audience then go back to the spectator and accidentally bump into them take the paper out of their back pocket and put your piece of paper in their. Ask them to name out loud what they wrote on the piece of paper. Then say how sure are you. Ask them to get the piece of paper out of their pocket and read out loud what they wrote on their.