"X Marks the Spot!" is a Sesame Street song about the letter X, sung by Sherlock Hemlock on The Muppet Alphabet Album, and later taped as a segment on the show. The items included in the song were an X target, a crossroad sign, an X-ray machine, a railroad crossing sign, a skull-and-crossbones sign which was a symbol for danger, poison and pirates. And finally, a xylophone.