what's going on here?

I was taking some shots of my d40, as I may put it up on ebay, this shot being with my 35mm 1.8 on my d90
http://gallery.photographyreview.com...m/DSC_2354.JPG

and this one being with the 50mm 1.8
http://gallery.photographyreview.com...m/DSC_2353.JPG

would the perceived fattening of the lens on the first pic be considered barrel distortion? I don't know much, scratch that, anything about the technicalities of lenses. Obviously to get similar distances, I had a shorter focal length with the 35 then with the 50. When I took two other shots on the tripod, I didn't notice the fattening that I got on the shots above (but never realized just how much of a short zoom the 50 is).

Completely normal. Heck most people who aren't photographers would't even notice any differences. A wider angle lens will distory the image more than a longer lens. Also your point of view is slightly different which is also contributing to the effect (outer edges of frame will have more distortion than inner)

yup yup! look how the edge of the printer curves differently as well. Just a biproduct of the lens selection.