Ant-Man is going to fit snugly into the Marvel Cinematic Universe, and may include appearances from several established characters. If the report below pans out then spoilers follow.
Latino-Review reports that early drafts of the Ant-Man script included a prologue in which Hank Pym met several notable characters at S.H.I.E.L.D. Among the faces are Howard Stark, Peggy Carter, Armin Zola, and young Alexander Pierce. Carter (Hayley Atwell) is preparing to spin-off into her own TV show Marvel’s Agent Carter, while Pierce was played by Robert Redford in Captain America: The Winter Soldier.