Sesame Street® 1st Birthday Invitations. Let Cookie Monster, Big Bird and Elmo help make your child's first birthday party an extra special celebration! Featuring Sesame Street's favorite characters, these Sesame Street® 1st Birthday Invitations are perfect for your party. Paper. (20 pcs. per set) Includes envelopes. Paper. 6 1/4" x 4 1/4" Sesame Workshop ©, Sesame Street © and associated characters, trademarks and design elements are owned and licensed by Sesame Workshop. © 2007 Sesame Workshop. All Rights Reserved.