The phrase "titular character" refers to the main character in a story, movie, or play. It is the character after whom the work is named or titled. Full definition
She went on to play the iconic titular character in «Bridget Jones's Diary,» and won an Oscar for her 2004 performance in «Cold Mountain,» opposite Jude Law and Nicole Kidman. (backstage.com)
But with his encore turn as the protagonist of Deadpool, Reynolds is now alone in the distinction of having played titular characters from both principal comic - book universes, Marvel (Deadpool) and DC (Green Lantern). (theatlantic.com)
But it was the original title for Gamecube that most will remember the ten centimetre tall titular character for. (gamesnosh.com)