Thanks for the head's up Lyford.
I'm curious though -- I recognized Sojourner, MER, but for me at least there were two mystery rovers. The one I was the most curious about was the solar powered, six-wheeled rover that was to the port and aft of MSL. The other was red and four-wheeled, located deeper into the photo and along roughly the same line of sight as the first (when it is visible).
Below is a screen shot of the rovers in question.Click to view attachment
Any thoughts? The six wheel rover was quite reminiscent of MER, but obviously different. My only guess -- and I don't even think it is a good one -- is a mock up of exomars???