From the Dr. Seuss Classic Book Characters Party Supply Collection. Dr. Seuss Postcard Party Invitations. Invite your closest friends and family to the wonderful world of Seuss with these colorful party invitations featuring none other than the Cat in the Hat and his mischievous blue haired friends, Thing 1 and Thing 2. Spaces are provided for name, date, time, place and RSVP. Includes 10 postcard style invitations and 10 envelopes. Invites measure 6" high x 4" wide. This product is officially licensed by Dr. Seuss Properties™ ©Dr. Seuss Enterprises, L.P. All Rights Reserved.