Factual error: After the Scarlet Witch forces Banner to become Hulk, he goes berserk in Johannesburg, South Africa. A few minutes earlier they were near the ocean at a ship scrap yard. Johannesburg is many kilometres away from any ocean.
Visible crew/equipment: At the end of the movie, when Captain America and Black Widow are walking towards the camera to train the new Avengers, the reflection of the cameraman's feet are seen on the glass railings in the back as they walk backwards shooting the actors.
Revealing mistake: At the very last (pre-credits) scene of the movie, as all the avengers are assembling, Scarlet Witch flies in, but it's not Elizabeth Olsen but a stunt double.
Answer: It's not an in-joke about real life. It's just a direct reference to Loki mind controlling him.
Greg Dwyer