I'm curious as well. I purchased the Pilot from Amazon Prime in HD and it is widescreen. I suspect that either it matches the DVD releases (season 1 wide while seasons 2 and 3 are OAR) or all have been converted to widescreen, but can't say for sure. I did compare the video quality of the pilot to what I have on DVD and did not notice much of a difference. They are likely from the same source, which could mean what is streaming is just an upconvert of the SD, or that it is an older HD master using older capabilities, or that the elements just don't have a lot more detail to provide.