Doctor Strange: 22 Secrets Revealed By The Director's Commentary
12. Ant-Man's Quantum Realm Is In There
There's a specific link to Ant-Man in the early scene where The Ancient One sends Doctor Strange spinning through the multiverse to blow his mind. Derrickson says that the realm that looks like lots of diamonds is a nod to the Quantum Realm from Ant-Man.
The director also mentions that the scene includes "a little bit of the horror director coming out" with the grotesque little hands that might have made some fans think of Return To Oz.
11. The Weird Motivation
Derrickson is clearly very motivated by strangeness: he says he made the movie "out of respect for those Lee/Ditko comics" and he generally acknowledges a general agenda to make every scene in the movie as weird as the weirdest scene in every other Marvel movie. He absolutely manages that.
At one point, the director also mentions his approach to using magic in the film was informed by a feeling that he thinks other movies thst deal with it rely too heavily on tropes. Take that Harry Potter.