(written from a Production point of view)
In a deleted scene from Star Trek Nemesis, Martin Madden was a Starfleet commander who would have replaced William T. Riker as first officer of the starship USS Enterprise-E in 2379. The character was named after Marty Madden, longtime companion of Nemesis screenwriter John Logan.
According to the scene, Madden transferred from the USS Talos to assume the duties of Enterprise first officer. The replacement was necessary as Riker had accepted an offer to captain the USS Titan and second officer Data was killed in action.
In the scene, Madden arrived on the bridge just as Riker was leaving. Madden, intent on making a good first impression with his new CO, Jean-Luc Picard, requested advice from Riker regarding Picard's attitudes. Sensing the opportunity for a good joke, Riker misinformed his replacement, telling him that Picard was very laid back and prefers to be called "Jean-Luc." Madden took Riker's advice to heart, and only after receiving a stare from Picard as a response did he realize that Riker was "pulling his leg." Picard later informed Madden that they were preparing to go on their first assignment, exploring the Denab system. Picard thought it would be interesting, adding that it was a place "where no one has gone before".
Madden was played by actor Steven Culp, who would ultimately be given the role of Major Hayes for the third season of Star Trek: Enterprise. Although Culp's scenes were not included in the theatrical release of Nemesis, they were partially restored for the DVD release, included in the "special features."
His existence is ignored in the Pocket TNG novels with the exception of Q&A in which he is depicted as being the first officer of the Enterprise in another quantum reality. The Picard of the prime universe had never heard of him.