Lego Thor Vs Superman was a film written in 2014. It takes place before the first Lego Superheroes film. It is unclear whether or not it will ever be completed.
Loki, the mischievous brother of Thor, arrives on Earth with the goal of recruiting villains to his cause. Clark Kent hears of Loki's escapades and goes out in search of this mysterious being. Superman had never seen an Asgardian before and his only lead was that Loki had arrived via a pillar of rainbow light. During Superman's search he stumbles upon Thor who had just arrived the same way. Superman mistakes Thor for the one causing mayhem and engages him in combat. Thor, offended, retalliates and the two get into a fight. Meanwhile, Loki meets with Lex Luthor at LexCorp. Loki gives him the motivation he needs to join his cause.