Bake and cool 1 in. high Thomas cake and two 1-layer sheet cakes. Position sheet cakes side by side on foil-wrapped base board. Ice smooth, upper half and sides in light blue, lower half and sides in light green. Use pattern to mark trees on cake top (reverse pattern for tree on right and make trunk slightly longer). Mark front and back tracks. Spatula ice track areas gray. Pipe brown parallel lines, ridged side up, for horizontal tracks: use tip 2B for front tracks, tip 47 for back tracks. Pipe band wheel rails, with tip 2B smooth side up for front tracks, tip 47 for back tracks.

For Thomas cake, outline face, facial features, bumper, panels and wheels with tip 3. Pipe in wheels, wheel caps, hitch, eyes, pupils, eyebrows, connector, inside bumper pads and inside of lights with tip 5. Cover cab, roof, bumper and underside of train and cab with tip 16 stars. Overpipe eyebrows with tip 3. Outline edge of lights with tip 12. Pipe tip 1 eye highlight and connector hole.

Position Thomas cake on sheet cake about 3 1/2 in. from bottom edge. Pipe tip 18 vertical lines to fill in tree trunks. Pipe tip 2A swirls for tree tops. Smooth edges of cake with spatula. Pipe assorted boulders next to tracks, using tip 12 and tip 8 dots to build out 1/2 in. to 1 in. wide from track. Pat smooth with finger dipped in cornstarch. Pipe tip 8 message with letters 1 in. tall, on waxed paper-covered board; set in freezer until needed. Pipe tip 5 bead border in blue on upper half of sheet cake. Pipe two rows of tip 352 pull-out leaves in green around bottom half of sheet cake. Pipe tip 2A swirled smoke, starting at Thomas cake. Position frozen letters on smoke.