It was a most Unexpected Party. Bilbo had no idea that he was going to be throwing it, for one thing.
But despite all the misunderstandings that Gandalf had apparently deliberately fostered (who says you can’t have a few laughs while you’re saving the world?), in the end, one bemused middle-aged hobbit with no prior experience at anything more challenging than walking down to the pub had agreed to travel halfway round the world with thirteen dwarves he didn’t know to steal things from a dragon. Because why not?