The guy on the right is defeated presidential candidate Mirhossein Mousavi. The guy on the left? Not sure who he is. But Fox News ran video of him at the big rally in Tehran today, and anchor Bill Hemmer identified him as Mousavi. Watch here. (Note that in a wider shot in the video a protester right next to our mystery guy is holding up a picture of the real Mousavi.)

Late Update: A TPM reader emails in to say that the guy on the left is Mohammad-Reza Khatami, and the resemblance seems pretty striking. So not a random protester, but another significant figure in the reform movement.