Here's an easy card to make for just about any occasion. I'm planning on using it for Mother's Day. It would also make a nice tea party invitation. On the back of the teabag is the message. Simple directions below.
White heavy card stock
Right click, copy and save to a program such as Word. Print out teacup template. It's designed to fit on standard letter size paper.
Cut out teacup and rectangle. Fold both in half so they line up as perfect as possible. Unfold.
Apply glue to teacup (refer to picture). Fold together. Let dry.
Cut out a piece of paper the same size as the tea bag. Tape the string to the paper. Cover up the string by taping the teabag to the paper. Tape string to the inside of the rectangle template and glue shut.
Write message on back. Hopefully your message will look nicer than the one above. Now just tuck the teabag/message into the teacup. Done.