This issue has now been resolved on iPhone, iPad and iPod touch. Please update to v1.9.16 or later to ensure the fix is installed on your device. A patch for users on Google Play and Amazon Underground is currently being tested and should be available soon.
Back to the Future content is not accessible in the game, even after purchasing the bundle.
This is a known issue which is currently being investigated by the Jetpack Joyride development team. A fix should be available by the end of November or early December.