Personalized Whatif Monster Youth Long Sleeve T-Shirt. What if you took that chance, and discovered just how great you are? Whatif Monster Youth Long Sleeve T-Shirt - Heather from the children's book, "Jonathan James and the Whatif Monster" by Michelle Nelson-Schmidt. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)