Here's a good example - a series, and probably not connected, of pictures suggesting that 'Doctor Who' co-exists with "Back To The Future".
Based on just these pictures, it would have been an adventure in which Doc encountered two incarnations of the Doctor - Tennant's Tenth and Smith's Eleventh, a perfect tale to be told during the fiftieth anniversary.
Here's an idea for a further complication: at some point during the story, the two time travellers had to take command of each other's time vehicle. I'm sure the Doctor would have had no problem mastering the DeLorean, but Doc Brown would have had to wing it at the controls. This is why I think this adventure would have needed River Song along for the ride so that she could help Doc out as his companion.
(More Wish-Craft: the Doctor would be teamed up with the now adult Marty McFly. And because of the Parkinson's tremors that Michael J. Fox has, they might delve into a temporal cause for his affliction. This could be why the Doctor had to get involved with Doc Brown again.)