This inventive pastiche of three well-known Dr. Seuss stories, with cameos by several others, celebrates the universally acknowledged truth that “a person’s a person, no matter how small” with a big, irrepressibly cheerful score that will captivate little ears. Standout performances include Kevin Chamberlin as the ruminative elephant Horton (“Alone in the Universe”); David Shiner, who shines throughout as the mischievous Cat in the Hat; and Sharon Wilkins, who uses her Aretha-sized pipes to call out the “Biggest Blame Fool.”