The story of Shrek, a beloved Ogre who falls for a princess, first brought to the big screen by Dreamworks, comes to life at Newton High School this coming weekend. The people behind Shrek The Musical, showing at 7 p.m., April 15 and 16 and April 17 at 3 p.m., have been preparing for this moment singing in the Oxford Youth Singers group. “It is a fantastic opportunity to express yourself,” said Lila McGiboney, who plays Gingy the Gingerbread Cookie.