"Of course we'd like to come - what shall we bring?"
"Could you manage a Hallowe'en-themed piñata?"
...and here we go.
(Oh, and the emergency? Version one, a papier mache construction failed. Four days of pasting and gluing, and it all went wrong. I didn't have four days left to make another that way.)
So, to the cardboard!
Step 1: The template
I had some thick corrugated card*, too thick for smooth curves, so I decided to go geometric, and make a truncated cuboid - six octahedra, in the planes of the faces of a cube, with equilateral triangles filling in the corners.
I used the largest handy sheet of paper (a page of newsprint) to make a square.
Folding into four, then a triangle, and cutting off one point makes a nice octahedron when opened.
I cut two "proper" octahedrons out of the card, then folded the template across the middle to make it narrower - I wanted the piñata to be slightly flatter than a cube.
*Saved from the box that a garden bench came in - Kitewife got fed up with waiting for me to get round to making her one.