The fat dragon is what really landed the movie for me. That? That was a DM decision, based on the players and the DM being memelords. Straight from the tabletop.
It really just demonstrated that the whole movie is a DnD campaign (agglomerate homebrew) with extremely high production value, and I LOVED EVERY SECOND OF IT.
Absolutely, the whole movie felt like that which was a big part of it's charm. Watching the first scene I could imagine the players asking the arrakoan chancellor's name, which the DM hadn't prepped, so he just made up Jarnathan on the spot..