This horrifying Instructable comes with 8 times the screams!!! I will creep you through the process of stealing files from Thingiverse and taking them into Meshmixer for a quick meshup and then out to your MakerBot!! or other machine.

Step 1: Getting the Models From Thingiverse!

Since they are posted there, I will give you links but also upload the files!

Ghost- There are 3 in the downloads but I went with number 3 because I liked its cute look.
Octopus - This one works great and can even help you turn your creation into a magnet if you like.

Step 2: MeshMixer!

Autodesk MeshMixer is free and now has a UI that is actually really helpful and useable! The link is included and MeshMixer takes OBJ and STL files.

Step 3: Bring Out the Dead, I Mean Bring in Your Models

To import your models into the program, you will use the import command on the upper left menu. I choose to bring the Octopus in first because that is what I wanted to fit the ghost around and it just seemed a bit easier in my head.

Your next step will be import your ghost when you select the Import command again a screen will pop up asking you if you would like append your current your model or replace it. In this case you want to append it, meaning add to it. You will also notice on the little dialogue box on the bottom right that it tells you how many different models are on your screen. This is important for a later step. If for some reason you don't see that option simply go to view and then select, Show objects Browser.

Step 4: Toggle Like Boggle

OK so if your like me, you will have noticed that when you brought your ghost in, it was upside down! Easy fix,

1) select the ghost file from the menu on the bottom right ( if you don't have that menu go back to step 3 )
2) make a selection on the model by using your painbrush under the selection tool on the left and just doing a small dab.
3) Choose modify -->select all from the select tool bar.
4) Choose Deform --> Transform from the same tool bar. This allows you to rotate and move the model using the 3 colored handles that come up. Each color represents an axis. If you click on the arrow you are moving your model on that axis if you click on the arch you are spinning it and if you click on the box you are resizing or scaling the model but only on that axis. Go ahead and move your ghost around until the mask is facing the correct way on the Octopus and then use the box's to scale your ghost to fit over the octopus head.
5) when you are finished be sure to select approve, if you are way out of whack and don't know how to correct yourself then you can hit ctrl+Z or you can simple click the Cancel button and it will return your ghost to the start position.

Step 5: Big Octopus

At this point I used the same process that I used for moving the ghost to scale up the octopus head so that they eyes looked out the hole. The process is below.

1) select the octopus file from the object selection dialogue box on the bottom right of your screen.
2) Select the entire octopus by using the select tool, painting a dab and then using the select all command.
3) Use the transform tool and use the box to scale the z hight making your octopus comically tall.

Step 6: Plane Cut

To make sure that the bottom of our model is optimized for 3D printing I am going to make a plane cut making sure to level all the pieces hanging down to be on the bottom level.

1) from the edit menu on the left you are going to choose plane cut.
2) Toggle the plane just as you toggled the model when you moved it leaving only a bit of orange showing on your model again remember we want everything on the same plane.
3) Select Accept.

Step 7: Combine!

Now its time to combine your two models. Select both models from your object select menu on the bottom right of your screen and then select the combine tool from the menu that pops up.

Step 8: Export.

Now its time to save and export your model for 3D printing.

1) select export from the left side menu and choose either OBJ, or STL to bring into MakerWare, (free software that runs your MakerBot)-NOTE: if you are not using a MB, obviously just choose the file that works best with your printer driver.
2) Now open in your print driver and away you go!!

Step 9: Printing.

I choose to print mine at high quality with purple and then painted it white with acrylic paint, if I had some around I would choose model paint because it provides a much nicer finish. I also thought it would be cool to print in transparent with a 1% fill so you could see the ghost image of the octopus. but that will have to be tomorrows task.

Good luck and Happy Halloween!!!