Years ago, when Batman vs Superman was initially the plan (I think 2003-2004), me and a friend were in a comic shop and were discussing what the JL movie should be like with the shop owner. We were obviously using Grant Morrison's first story arc as the JL movie story.
Finally, after a lot of discussion, we formulated an end credits scene as well. At the end of the credits, after the JL has successfully defeated the white martians, we cut to a place where we see a guy sitting on a throne. Desaad stumbles into the room, and he says "My liege, our plans for invading Earth have run into problems. The Earth has its heroes now". We then see the guy stand up from the throne, walk to Desaad and say "The dark side will reign supreme", and cut to Darkseid's laughing face.
After watching "The Avengers". I texted my friend immediately saying "Our end credits idea has been stolen".
It is amazing just how much Avengers actually follows the JLA arc if you think about it.