Avengers: Age Of Ultron - 32 Easter Eggs, In-Jokes And References
25. Worthiness
As shown in the pre-release teaser footage, the Avengers talk about the issue of worthiness in relation to Thor's hammer, with each taking turns to try and move it.
Interestingly, Clint Barton refers to the hammer as being "a trick... a circus sideshow", which feels like a reference to the comic books that have Hawkeye learning archery from traveling circus performers.
Cap does manage to budge the hammer slightly, nodding to his worthiness in the comics. Everyone else fails, but Natasha declines, saying it's not a question she needs answering. That's not accidental: in a What If arc in the comics she is deemed worthy and becomes the Goddess of Thunder.