***POSSIBLE HUGE SPOILERS***
Read on at your own risk
This has to be taken with the Sifto-est grain of salt, but it does come from TotalFilm which are usually quite credible. The site is reporting from British actress Jenny Agutter (mostly known to fanboys as "the chick" from Logan's Run) that another Marvel superhero, one nobody could've expected, will be swinging by for a quick pop-up in the Joss Whedom geekgasm of a film.
Says the lady,
"I’m sworn to secrecy. I wasn’t allowed a script until I got there, and when I did I felt like a complete child being on big sets and a huge parking lot full of Winnebagos," adding that one of those winnebagos, right besides Iron Man's, was reserved to said cameo and sported the associated colors.
Such a prospect had never even occurred to fanboys all around since another -greedy- studio owns the rights to that character; heck, Warner wouldn't even allow Bruce Wayne to be hinted at in Smallville, even though they own both! BUT this is a Joss Whedon film, grand master of the Order of the Geek, and beside that superhero has his own film opening a bit after Avengers so why not just use the free publicity? The studio needs him to be a big hit, after all.
If you haven't guessed already and still wanna know, the character in question is This Guy.