In a movie with a lot of A-list actors there is bound to be ego-clashes. However, for now, Avengers seems to be different as some of the lead actors are good friends. so much so that they decided to get inked together.
According to Entertainment Weekly, the tattoos were originally Johansson's idea. She and Evans started the trend in New York; then she brought the artist, Josh Lord, to Los Angeles to ink up Downey Jr. and Renner. Downey Jr. told EW that they eventually "bullied" Hemsworth into participating, but Mark Ruffalo opted out.
The five members of the cast now sport a simple Avengers symbol intertwined with the number six — but they're not the only ones. After getting inked, the actors turned the needle back on Lord, and each contributed to their own version of his tattoo, which Downey Jr. described as a "total massacre."