Avengers: Age Of Ultron - 32 Easter Eggs, In-Jokes And References

16. Black Widow's Vision

Natasha's vision is the most loaded other than Thor's as it finally fleshes out her story a little more and pulls back the curtain of mystery surrounding her.

The flashback references Widow's comic book origin that saw her introduced as a ballerina subjected to mental conditioning and experiments (including, heart-breakingly, ceremonial sterilisation) at the Red Room Academy - which she name-checks in the film.

Julie Delpy plays her sinister former mentor, while Nick W. Nicholson plays the creepy, but very brief Dr. Taryl Jenkins.