Thomas the Tank for my son's 4th b-day.  When the kids arrived, they received a good size card board box to decorate. There were cut out pieces of construction paper in wavy lines and circles of all different sizes to put on these boxes. There was also some twine attached so that once the boxes were decorated, they could put on their "train car". The yard was spray painted like a railroad track (grass grows fast so it would be gone soon enough). An appliance box was painted up to look like a train station and a railroad crossing sign was there.  I played the song, "Little Red Caboose" and handed out their party favors, an engineer cap and train whistle (put names on both!).  They went around the track slow, fast and then slow again with the music.  We then played pin the caboose on the train and "Engine, Engine, Caboose." Then we moved to eat the "train" cake. Yellow cake made in miniature oaf pans.  Dyed the icing different colors and painted each train a different color. Oreo's were the wheels and miniature oreos were made into a smoke stack for the engine. M&M's and oreos were also used to decorate cargo trains. Too cute!! At the end each child had their cap, whistle and a Thomas the Train certificate.  Real fun and real easy!