Calvin comes in with a couple envelopes and says one is for Hobbes. Hobbes is so happy, since he never gets letters. He looks at the envelope wondering who could have sent it and what could it be. Calvin yells for him to open it and calls him a lunatic. Hobbes tells him not to get huffy and that he wants to savor this.

Hobbes looks at what he got in the mail. He says it's an invitation. Calvin wants to know who would invite him anywhere. Calvin says no one invites a tiger because you can't get the insurance. Hobbes says someone is inviting him. Calvin shouts for Hobbes to tell him who invited him and to read the invitation. Hobbes figures it's probably some big state dinner. He hopes he can find his cummerbund.

Calvin continues to badger Hobbes about his invitation. He asks what it says and calls Hobbes a dumb hairball. Hobbes tells him he'll read it when he's good and ready. Calvin burns with impatience. Hobbes starts reading his invitation....slowly. Calvin yells at Hobbes to read faster.

Hobbes reads that it's an invitation to Susie Derkins' birthday party. Calvin asks if it talks about him, and Hobbes says no. Calvin thinks his invitation must have been sent separately. Susie probably insured it so it wouldn't get lost. Those invitations take longer to arrive. Calvin figures he'll have to sign for his invitation when it comes. Hobbes notices something on the back of the invitation. Susie wrote that Hobbes can bring "that stupid kid you hang around, if you must".

Hobbes celebrates being able to go to the birthday party. Calvin calls Susie stupid. Hobbes talks about the balloons, cake and presents. Calvin says Susie won't be getting a big present from him. Hobbes figures they'll play games, too. With a smile on his face, Hobbes suggests they might play "spin the bottle". Calvin yells for him to "get real".

Hobbes is making out a list of gifts they could give Susie. Calvin suggests a mouth full of broken teeth. Hobbes thinks a can of tuna fish would be better. Calvin wonders why she'd want that. Hobbes figures maybe she wouldn't want it, they could offer to take it back, get some mayo and bread...

Calvin and Hobbes are walking to Susie's party. Calvin has a gift in his hands. As they approach her home, Calvin says this is their last chance to not show up and have a new bike horn.

Susie opens the door, and Calvin hands her the gift. She thanks them for coming and they step inside. She notices Hobbes is wearing a tie. She picks him up and hugs him. Grudgingly, Calvin tells Hobbes that he was right about girls flipping for ties and that he can stop winking at him.

Susie has a scavenger hunt at her party. Off go Calvin and Hobbes for the first item, an old license plate. Calvin remembers seeing one on their way over to Susie's. He pulls out his Swiss army knife and starts to remove the plate from a car. Hobbes wonders if this game is legal.

Susie hands Calvin a paper plate for his piece of birthday cake. Calvin whispers to Hobbes that he hopes the cake is something good and not gross like coconut. Hobbes tells him not to worry, the cake is chocolate. Calvin asks if he saw the cake. Susie yells that someone cut a piece out already, and that she didn't even get to blow out the candles. Hobbes whispers that it's nice and moist, too.

Susie thanks Calvin and Hobbes for coming to her party and for her gift. Calvin and Hobbes are walking home, and Calvin stops. He digs into his pocket while something puddles up on the ground. He says Mom may not want the piece of cake and ice cream they're bringing her.