Jonathan Gems is a British playwright and screenwriter. Gems wrote part of the screenplay for Batman. He wrote the script while the film was being shot at Pinewood Studios along with Warren Skaaren and Charles McKeown, since original screenwriter Sam Hamm couldn't participate at that time due to a writer's strike.
He wasn't credited for his work on Batman.
Gems is best known for his collaboration with director Tim Burton for Mars Attacks!, for which he wrote the screenplay and the novelization. Gems has written a number of unproduced scripts for Burton, including a sequel for Beetlejuice titled Beetlejuice Goes Hawaiian, an adaptation of Edgar Allan Poe's "The Fall of the House of Usher" set in Burbank, California, The Hawkline Monster, a cowboy/monster movie that was to star Clint Eastwood and Jack Nicholson and Go Baby Go, a movie in the style of Russ Meyer.
Other works of Jonathan Gems include White Mischief and The Treat (also director).