We had Clifford the Big Red Dog (a fantastic theme) for my son's third birthday.  I first made our own invitations that had a big picture of Clifford on the front with a call-out saying "Woof! You're Invited to \*\*\*\*\*\*'s Third Birthday Party" and inside it read… "Please Join Us For A Dog Gone Good Time" with doggie footprints everywhere. We rented out his playgroup center for a few hours so all the children (ages ranging from 10mths-5yrs) would be happy enough to play together.  For our activities I made a balloon shaped Piñata with doggie paw prints and bones all over it. (I didn't think Clifford's head would be appropriate to hit) I gave each child a large red plastic cup to collect all the goodies for when it broke open.  We also had Pin the Tail on Clifford, which was a huge hit.  I found a picture of Clifford and took it to my local copy store to have it enlarged to life size, then painted it red and used construction paper to duplicate tails.    Next we had a treasure hunt to find Clifford's bones. Before the party started I had Daddy hide all the bones in different places high, low, under and on top of toys for the children to find.  To make these, I cut out 50 or so bones from brown construction paper and taped a piece of candy to each bone using double sided sticky tape.  Great game for all ages!  On an activity table in the corner I had made my own red play dough with a few doggie related cookie cutters. And on another table I had a few pictures of Clifford with red crayons, pencils and glitter for them to decorate.  Great for the smaller ones! Our menu consisted of hotdogs and using cookie cutters.  We had bone shaped brownies and Clifford shaped cookies, among other simple party food.  Our decorations and favors were all ordered from BirthdayExpress.com.  Made it very easy as I live overseas and can't "pop" into my local dollar store.  At the end, my son was proud to hand out his favor boxes to each of his friends.  They all went home happy and dog gone tired!!!