In the scene, in the first few minutes of Iron Man 3, Aldrich Killian stops the couple in an elevator to propose his think tank and Tony tells him to meet him on the roof. If you take part in this “challenge,” when the clock strikes midnight the hero will say “Hey, Happy New Year!” with you right after talking research with Maya and being randomly pounced on by Happy.
Article source: https://www.cinemablend.com/news/2464299/take-the-iron-man-3-new-years-eve-challenge-with-robert-downey-jr