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Peekaboo (also spelled peek-a-boo) is a form of play played with an infant. To play, one player hides their face, pops back into the view of the other, and says Peekaboo!, sometimes followed by I see you! There are many variations: for example, where trees are involved, "Hiding behind that tree!" is sometimes added. Another variation involves saying "Where's the baby?" while the face is covered an... Wikipedia