It seems like all little boys goes through a phase when they like trains, and it seems like a lot of them love Thomas the Tank Engine. Our friends' little boy is one of those kids, and his birthday party this year was Thomas themed. (He's the same one who had the Little Einsteins cake last year.) I've done a few Thomas cakes before, and thankfully they get easier each time :-)
I wish I had remembered to take my camera (or iPhone) to the party, it was at one of those indoor inflatables places, and I think the adults had as much fun playing on those things as the kids did.