Rick wakes up from his Coma. Its all been a nasty nasty dream. But Shane was was and is still plowing Lori. AMC takes the easy way out.
Well, there could be precendent based on one of the comic books that had a kind of twist bonus ending:
This issue came with a bonus ending that is not canon to the official story. In the ending, Rick had recently been hit over the head by Michonne. For reasons unknown, Rick explodes and wakes up in a scientific infirmary. Rick notices his missing hand has been replaced with a robotic one. Putting on armor he finds, he falls out of a sky ship. He sees Glenn being torn apart by a zombie and then finds himself before Tyreese, Axel, and Martinez.
Michonne appears and explains how three weeks ago, Rick had suddenly disappeared. Days after, aliens came to invade, and he explains how they planned everything; reanimating the dead and destroying civilization. Their plans were to use the remaining humans to harvest water, which they apparently use for currency on their planet. The remaining humans, however, decided to fight back.
Soon, Michonne is killed by The Governor (who is a cyborg) who crushes her head with a mechanical arm. Lori can be seen crying, holding onto The Governor's leg. He explains to Rick how he is either to join him or die.
It was explained in the letters section how many readers actually believed this to be actual canon to the story, to which it was dismissed to just be for a bit of fun.