MCU: 15 Majorly Dumb Plot Holes You Never Noticed
2. How Did Thor Get Back To Earth? - The Avengers
In Thor, Loki vows to make his father, Odin the All-Father, proud by destroying Jotunheim; the home of his Agard's most recurring enemies. Because the Bifrost bridge serves as a conduit that connects The Nine Realms, Thor's demented stepbrother uses its power to send a lethal laser through to Jotunheim, decimating the world.
Thor realises that the only way to stop his sibling from destroying the planet is by shattering the Bifrost. Even though the god of thunder is fully aware this will prevent him from travelling to Earth, he smashes the Bifrost with his enchanted hammer, breaking it apart.
So how did the prince of Asgard come to Earth in The Avengers? The movie explains this plothole in two words; "dark magic". That's it. This moment completely contradicts the ending of Thor and the best the writers could come up with is "dark magic".
Director, Joss Whedon, knew this was a problem and decided to introduce Thor last, believing fans would be so happy to see all The Avengers together for the first time, they wouldn't notice this inconsistency... which they did.