Board Thread:Spoilers!/@comment-24674051-20150626172312/@comment-24936039-20151013002350

Merlin is impersonating Lancelot (which would explain how he was able to be in LWM as the 'usher' to warn young Emma not to pull the sword out of the stone).

As been pointed out by others, magical using villains often disguise themselves as others to trick the heroes. So, perhaps King Arthur and Guinevere are also disguised villains (Mordred and Morgana perhaps) which would explain why they don't want the Storybrooke heroes to talk to Merlin in Tree form (and maybe the Tree is not really Merlin but Lancelot...)? Not to mention King Arthur convincing his henchman to steal the magic items (and the non-existent bean) and make the ultimate sacrifice in Storybrooke Jail to convince the heroes that he's a good guy.