My Daughter wanted Blue's Clues for her 4th birthday party.  I made the invitations with some Blue's clues clip art around the edges.  In the middle it read "GUESS WHO'S TURNING FOUR?" Then next to a blue paw print a clue:  A picture of my daughter. The guest arrived to find our mailbox decorated like MAILBOX.  I used felt to wrap around the box and made the face out of felt also. Looking out the window was Blue herself (the very large head and paws from my daughter's blue's clues sleeping bag) This could be made from poster board too. And leading down the driveway where blue paw prints made from poster board. For the cake I made a handy-dandy notebook. Cut a sheet cake in half. Lay the two halves about an inch apart on a cake board. Use licorice to connect the two pieces to look like the ring binders of the notebook.  The notebook read like the invitations : GUESS WHO'S TURNING FOUR? Then a blue paw print made of icing and next to it a picture of my little girl (placed on a piece of cardboard and outlined with icing). Everyone thought the cake was so cute. The party favors were blue's clues key chains, bubbles. etc. You can also buy a pin the flag on mailbox game at the party stores. It was a fun party!