 The film was promoted at the 2010 San Diego Comic @-@ Con International , during which a teaser trailer narrated by Samuel L. Jackson was shown followed by an introduction of the cast . In June 2011 , Marvel Studios announced that it would not hold a panel at the 2011 San Diego Comic @-@ Con International after studio executives decided it was not prepared to compete with its own past and fan expectations with filming still in production . In July 2011 , a teaser trailer that was meant to be the post @-@ credits scene of Captain America : The First Avenger was briefly leaked online . Entertainment Weekly speculated it came from a preview screening and described the footage as " shaky , fuzzy , flickering and obviously filmed on a cell phone " . 
