Saw this on the tfw2005 website yesterday. Both Mudflap and Skids have running changes, to be more movie-accurate now that the movie has been released. This is bound to annoy some who have already bought both, and would have prefered to have more movie-accurate toys if they had known about this earlier.

Mudflap - first run had 'Trax' on the numberplate, which is the car model, but Skids had his name on the numberplate. In the movie, apparently, Mudflap has his name on the numberplate, and it is a bit confusing that one twin has his name on the toy and the other doesn't. Now a later release of Mudflap has the name 'Mudflap' on the numberplate, but I haven't had a chance to check if any of the ones in our stores yet are of this later production run.
But at least you can tell in packaging, which version is which, before you buy it.
http://www.tfw2005.com/transformers-...ariant-168024/
(scroll down a little for a clear photo of what the numberplate looks like)

Skids - first run had both teeth painted silver. Later, they coloured one tooth gold to match the movie. I don't think they must have done many unpainted ones, because I got mine at BotCon, which was a fairly early release of that wave - and it actually has the gold tooth (I'm relieved by that).
But this one is not easy to spot in packaging though, becaus the robot head is inside the cabin of the car mode - but apparently some have said they can still just see it (some mentioned using a torch for better viewing). Unfortunately, this is the only definite way of getting a gold-tooth version, as the production numbers some have been listing in the following links aren't guaranteed. And people are even finding Skids toys with no paint on their teeth (teeth are green).
http://www.tfw2005.com/boards/transf...d-numbers.html
(photo of the unpainted version is shown in the link above)
http://www.tfw2005.com/boards/transf...ted-teeth.html

Happy hunting...