During the Credits
There is an extra scene about half way through the credits of Doctor Strange that teases certain characters showing up in Thor: Ragnarok.
Doctor Strange (Benedict Cumberbatch) is shown meeting with Thor (Chris Hemsworth).
Thor says that he needs help from Loki to trackdown his father, Odin. Then just as Thor is getting close to finishing his beer, Dr. Strange refills it and says, “I keep a watch list of individuals and beings from other realms, that may be a threat to this world. Your adopted brother Loki is one of those beings. So… why bring him here to New York?”
The two make a deal to find Loki and Odin under the condition that once found they must be returned to Asgard for good — which will presumably be continued in Thor: Ragnarok.
After the Credits
There is also a stinger after the credits of Doctor Strange.
In the extra scene after the credits, Mordo confronts Pangborn (Benjamin Bratt) to explain that he’s had the revelation that the true purpose of a sorcerer is to twist things out of their proper state, steal power, and prevent nature such as Pangborn.
Mordo then removes Pangborn’s power and re-paralyses him, revealing that what is wrong with the world is too many sorcerers and suggesting he’ll be making more de-powering trips in the near future, of course, setting up the sequel.
Special thanks to mumbles and Jezamiah for the stinger submission!