McElligot's Pool is a children's book written and illustrated by Theodor Geisel under the pen name Dr. Seuss and published by Random House in 1947. In the story, a boy named Marco, who first appeared in Geisel's 1937 book And to Think That I Saw It on Mulberry Street, imagines a wide variety of fantastic fish that could be swimming in the pond in which he is fishing. It later became one of the Seuss books featured in the Broadway musical Seussical where its story is used for the song "It's Possible". Plot The story begins with a boy named Marco fishing in a small, trash-filled pond known as McElligot's Pool. A local farmer laughs at the boy and tells him that he will never be able to catch anything. Nevertheless, Marco holds out hope and begins to imagine a scenario in which he might be able to catch a fish. First, he suggests that the pool might be fed by an underground brook that travels under a highway and a hotel to reach the sea. Marco then imagines a succession of fish and other creatures that he might catch in the sea and therefore the pool. He imagines, among others, a fish with a checkerboard stomach, a seahorse with the head of an actual horse, and an eel with two heads. When Marco is done imagining, he tells the farmer, "Oh, the sea is so full of a number of fish, if a fellow is patient, he might get his wish!" Creation Geisel painted some of the water colors that illustrate McElligot's Pool while vacationing with his wife, Helen, at the summer home of their friend Kelvin Vanderlip, in Southern California. The book was the first Dr. Seuss book to use water colors for its illustrations, but because of budget concerns, Random House published half of the book in black and white, alternating between two pages in color and two pages in black and white. Marco, the book's main character, first appeared in And to Think That I Saw It on Mulberry Street, the first Dr. Seuss book published in 1937 by Vanguard Press. Geisel dedicated the book to his father, whom the dedication refers to as "the World's Greatest Authority on Blackfish, Fiddler Crabs, and Deegel Trout". According to Dr. Seuss biographers Judith and Neil Morgan, "deegel trout" was a private joke between Geisel and his father that