Avengers: Age Of Ultron - 32 Easter Eggs, In-Jokes And References
21. The Crimson Cowl
When Ultron upgrades and heads to Sokovia to enlist the Twins' help, he first appears to them under a red cape, which is clearly a reference to his first appearance in the comics when he went by the alias the Crimson Cowl.
The rest of his appearance is based on elements from the comics. In his first broken puppet prototype form, one of the broken Iron Man suits he uses looks suspiciously like the black and gold coloured Model 42 armor from the 2013-14 Marvel NOW! arc.
The majority of that body is an Iron Legion drone - specifically number 05, which is clearly a reference to the character's original name: Ultron-5. The glowing eyes and mouth of that prototype (before he gets his movable facial parts) is also an homage to his original comic appearance.