Check out this video of a couple of bearded dragon lizards waving to each other across the pet shop. What do you think they are trying to say to each other? See my explanation of what's really going on below.
While it's easy to imagine these two lizards saying "hey bro!" or "howyadoin'?" what they are really doing is showing submission. Younger and smaller bearded dragons do this arm waving behavior to let older, bigger or more dominant lizards know that they are no threat, which minimizes the possibility of aggressive interactions in which they would most likely lose out.
Pet bearded dragons might even do it towards people or other larger pets if they are feeling intimidated.
Photo by psyberartist via Flickr Creative Commons.