Marvel Studios is planning a standalone movie featuring The Hulk as part of ''phase three'' of its comic book adaptation project.Bruce Banner and his green-skinned alter-ego - played by Mark Ruffalo - will receive a solo film after 2015's sequel to superhero ensemble 'The Avengers'. 'The Avengers' sequel will see the Marvel Universe's Illuminati ship the Hulk into space, setting up the scenario for a film based on 'Planet Hulk'. The original comics storyline centred around the character pressed into service as a gladiator on an alien planet. 'Avengers 3' is then claimed to adapt 'World War Hulk', the subsequent crossover in which an enraged Hulk returns to Earth and battles the combined forces of Marvel's heroes. Hulk is not expected to appear in any of Marvel's upcoming Phase Two films until Joss Whedon's next 'Avengers' outing. Ruffalo has previously expressed uncertainty over whether a solo outing would happen. He said: ''I think they've done it. I think they feel that they've done that. I think they don't really know where to go [with the character].''