First I just made the cake out of a chocolate box cake in my 11×15 sheet cake pan.
I made my Wilton’s buttercream icing (wilton.com) and made 3 batches of it, just so I had enough. One batch I made the thin consistency to ice the cake and the other 2 were the medium consistency for the star tips. I crumb coated the whole cake first, with a thin layer of icing to cover crumbs. Let cake sit out so icing would harden a little, then covered it with a final thick layer of icing.
My husband drew with a tooth pick, each character very lightly in the icing. Then after, I went over it with Wilton’s Black icing in the tube, using round tip #3.
After I had that all outlined, I then mixed my colors using Wilton’s food coloring. I mixed a cup of pink and set it aside, a cup of yellow, a cup of light blue, and a cup of purple.
I used star tip #16 to fill in ALL of the characters. Took me about 5 hours, slowly working on it non-stop.
I then bought Wilton’s already made fondant (pastel colors) and bought the small ABC/123 fondant cookie cutters, and made the “WOW! WOW! CHLOE’S 4!” out of that. I used the same star tip #16 to make the yellow zig-zags around top of cake and the grass tip to make grass around bottom of cake. It used star sprinkles to add a colorful touch around words.
All in all it was pretty easy, just took time. Good Luck!