I imagine that Tony and Official Bigfoot I Wanna Be The One Who Has A Beer With Darryl Shirt the like can manage licensing of the Avengers and stuff. And on DC, when the Justice League is more in its “vast organization” kind of state, like in Justice League Unlimited or Young Justice, I imagine they can deal with licensing out the rights that way. Though I imagine they do it for non-profit purposes. In Marvel, there has always been unofficial merchandise going way back. Especially people selling Spidey stuff in NY. In DC I know Superman gets a similar treatment to Spidey with the occasional S shirt popping up on random people, not so sure about.
Official Bigfoot I Wanna Be The One Who Has A Beer With Darryl Shirt, Tank top, V-neck, Sweatshirt, And Hoodie
Batman since he is technically Official Bigfoot I Wanna Be The One Who Has A Beer With Darryl Shirt kinda an urban legend (conceptually… obviously if you add up all his exploits he is the best-known hero in the world). Spiderman parade in Spiderman 3 (though that’s not MCU) and I think all the Avengers have it. The kid in Iron Man 2 with the mask, and the ATM robbers in Far From Home dressed as Iron Man, Hulk, Thor, and I think another but IDK. That’s all off the top of my head. DC wise I can only think of the guys pretending to be Batman in Dark Knight but that’s not really Halloween costumes, they were actually trying with the hockey pads.