13. The Return Of The Ten Rings in Ant-Man
If you saw the first Iron Man movie, you might have become aware of the terrorist organization called the Ten Rings. One man showed up in the first Ant-Man movie to try and buy some Pym particles from Darren Cross (the main antagonist), who was sporting a Ten Rings tattoo on his neck. It was definitely a callback to the first movie and demonstrated that the organization hadn’t been beaten after all and was still very much alive. Who knows if they’ll show up in the future MCU movies.