Matt Damon has joked he wants to make a pornographic version of the 'Bourne' trilogy.The 36-year-old actor - who has reprised his role as former CIA assassin Jason Bourne for the third time in 'The Bourne Ultimatum' - suggested director Paul Greengrass should try making the action franchise X-rated.When asked about Bourne the musical, he quipped: "Bourne the musical. That was my suggestion. I think you have to kind of change the genre. It's either got to be porn or a musical to re-ignite the franchise."Matt then launched into spoof song from the proposed musical, singing: "They're chasing me, they're chasing me holy f***ing s**t."The star also compared the previous DVD extras from the past two movies, 'The Bourne Supremacy' and 'The Bourne Identity' to "dog s**t". He said: "One of the DVDs came out and it said explosive extra scenes and it was all these scenes that were not good enough to be in the movie. It's kind of like walking into a house, holding a bunch of dog shit and saying, 'Hey look what I almost stepped in.'"I've seen the extras for the next DVD and they are very good. There is more behind the scenes footage."