I go forward in time, find a museum dedicated to this current era and stand really still by one of the displays so that people would think I was actually part of the display. Then when people came around saying things like "heh, his cellphone is just a cellphone, how cute and stupid they were" I'd just out of the display at them screaming like a maniac to give them a good scare. Then I'd take them to an ever further future to a museum dedicated to their time to try and show them that to the people of the future the people of the past are always cute and stupid.