Of course only Merlin could accidentally sleep over one thousand years, missing two World Wars and only waking up after the end of a major Wizarding War. Where is a warlock to go when he needs to learn about everything he's missed? Why Hogwarts of course! Watch the Golden Trio meet the world's most powerful Warlock (not that they know that of course!) in their 7th year of Hogwarts

This is what happens when Arthur takes it upon himself to help Merlin find the true meaning of magic. Complete and utter crack. Written for a challenge issued by BriefShiningMoment.