8. The Infinity Stones
Doctor Strange is so strongly associated with the Infinity Stones - or Infinity Gems, as they're more traditionally known - in the comic books, that simply including them in the Marvel Cinematic Universe was undoubtedly foreshadowing the character's arrival in the franchise. As a member of Marvel's Illuminati, Strange has been the guardian/owner of the Soul Gem in the comic books and the likelihood is that the Marvel Cinematic Universe version of that particular item will make its first appearance in Strange's first solo movie - and that means Marvel Studios will have been planning that since the introduction of the first Infinity Stone (the Tesseract) in the post-credits scene of 2011's Thor. Strange will undoubtedly go on to play a huge part in the Avengers: Infinity War movies - probably exhibiting a great knowledge of the Infinity Gauntlet and the six Infinity Stones it holds - and, as such, it's fairly obvious that their inclusion in the franchise was always with him in mind.