Has any series of books in history inspired as many spinoffs as the extended universe of Lord of the Rings? I guess that anything Hogwarts-related could be considered a big competitor, but there are more books in the series to draw from there. Also, as any diehard Tolkien fan will protest little compares to the rich and detailed worldbuilding that has gone into Middle-earth over the years. It is undoubtedly a big part of the reason that it has been responsible for one of the most longstanding and continuously flourishing meme communities that has ever graced the internet. LOTR memes are a genre that never stops being fun, as it is always interesting to see the new ways in which the fandom will interpret and create humor with the same material that they first fell in love with many years ago. It is a legacy that Tolkien could be proud of.