To make the fridge magnet variation you will obviously need a magnet.
You will also need some release agent to remove the magnet prior to baking. I used some KY Jelly, just remember to pull a really big grin at the cashier who sells it to you to see who will blush first.
Start the tentacle cone as usual, but this time when the wide end starts to form press the lubricated magnet into it.
Finish the tentacle as usual and form it into the desired shape.
To remove the magnet take the stack of magnets and place it against the base, they'll stick and you can pull it out, leaving a hole the right size. Once baked you can glue the magnet back in to the hole.
Make four and arrange them on your fridge in interesting patterns.