Draw out the card template on your sheet of yellow card: 21 cm long and 6.5 cm wide. Pencil in where the folds will be - there will be 3 x 6.5 cm squares plus a little bit on the end for taping the card shut.
Cut out each of the cards, making sure to leave the little edge to tape the card shut.
Valley fold along each of the lines.
Cut out one 6 cm square for each card. Cut out one 6.0 x 7.0 cm rectangle for each card too (not pictured).
Go to Google Images and search for a 1UP image to your liking. Save to your computer. Open a Word Document (or equivalent) and insert the image manually selecting the image width to be 6.0 cm. Copy the text boxes and paste next to each other to fill the document if you are making many invitations. Print off using photo paper, selecting the highest quality ink setting.
Cut out each of the 1UP mushrooms leaving a 1 cm white piece on the bottom. Glue to the 6 cm square yellow craft card and cut out.
Affix a piece of double sided tape to the back of the bottom edge of the 1UP mushroom. Set aside for now.
Download the Plumber Brothers font, link is in post above. Open another Word Document and create a text box 6 x 7 cm. Using the free font, write in your birthday party details. Make sure you include a PULL HERE along the bottom edge. Print off on photo paper and cut out. Glue the printed photo paper invitation to the 6 x 7 cm piece of yellow craft card.
Cut out one 5 cm x 15 cm strip of plastic per invitation.
Add a piece of double sided sticky tape to the bottom edge of the plastic. Line up the plastic under the first square section of the yellow craft card you cut out earlier.
Stick the two edges of the plastic together with the double sided tape, loose enough so that the plastic will slide. Keep the join near the top edge.
Add a piece of double sided sticky tape to the top of the invitation card. Make sure the length of this tape is shorter than the width of the plastic (or else it won't slide open!).
Remove the paper off the double sided sticky tape on the invitation print out. Place the card onto the middle section of the folded card, top edges aligned. The PULL HERE will be visible peeking out the bottom. Fold over the side with the plastic. The sticky sided tape will stick to the plastic near where the join is on the back. Remove the paper on the double sided sticky tape on the 1UP mushroom and place on the plastic with the top edge of the mushroom aligned with the top edge of the card. Press firmly to stick together.
Affix a piece of double sided tape to the edge flap on the card and stick shut. I just folded it over the back of the card, but you could tuck it inside underneath the plastic layer, if you wanted.
Open another Word document. Search Google Images for the Super Mario Question Mark, save to computer, and add image (you may need to crop the size first) so it is 5 cm in width. Print off on photo paper or white craft card, cut out and glue to the front of the card. I added a short length of white string to the top of the 1UP mushroom to help open the card, as I found the plastic did not slide well without it.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.