This is a prop I built for a Star Wars party. I didn't want to spend a lot, but I did want it to look cool.
I know that there are some incredibly talented folks who put years of effort into making awesome R2D2 and other droids, but I wanted something inexpensive and I only had a few months until the party. So rather than use sheet metal and fiberglass, I used mostly cardboard and wallboard joint compound. I also use a lot of stuff that I had in my junk-box.

Yep - that was once a used refrigerator box!

Step 1: R2D2 Frame and Covering

I found some pictures on the web and once I found the overall dimensions of R2D2, I was able to calculate the size of each piece. R2D2 is about 43 inches tall and the body is about 18 inches in diameter (not counting the legs)
Google image search is great!

Here's a site that I found very useful: (especially the Autocad .DXF files)
http://files.astromechbuilder.com/attachments/?dir=/*2003_Archives/9-September_2003

also:

http://starwars.wikia.com/wiki/File:ArtooBlueprints-SWBTUC.jpg

I acquired a few refrigerator boxes at a local retailer and got to work.
I created a frame for the body, then wrapped the cardboard around the frame.
This is a bit tricky. You'll need to soften - but not drench - the cardboard by spraying it with water and letting the moisture soak through the layers. When it's sufficiently soft, you're ready to wrap it around the frame. Apply hot glue to the edges of the frame and attach the softened cardboard sheet to it. I recommend that you get some assistance with this step.
It has a few inconsistencies, but we'll compensate for that later.

Step 2: Cutting Out and Assembling the Legs

The legs are also made of cardboard, so I drew an outline on the cardboard an cut out a total of four duplicate pieces. I left a lot of extra cardboard at the bottom since I wasn't quite sure what I wanted to do with the bottom of the feet.
I then assembled the leg with several long strips of cardboard, softened as before, and wrapped around the sides of the leg. Patience is key, letting the softened cardboard form to the shape that you want. I'm getting better with the use of the hot glue gun!

To help keep the two halves of the leg separated by the proper distance, I tacked in a 2x4 piece of lumber temporarily between the two halves of the leg.

I later ended up gluing a 2x4 in permanently, but it was oriented so that when assembled with the body, I could put a long wood screw through the wood, and securely attach it to the body -- which had another piece of wood glued into it's inside.

The cardboard however, has an un-mistakable look of... cardboard. I decided to cover the legs and the body with wallboard joint compound and sand it flat. This covers a number of goofs and bumps.

Step 3: The Body - Altering My Plans

My inspiration for creating this project was partially from an R2D2 promotional Pepsi beverage cooler that I saw while doing a Google image search. The body of the beverage cooler went all the way to the ground which makes sense for the cooler, and was a simpler design. This is what I intended to do, but I changed my mind and decided to make it more like the real R2D2, so I cut off the bottom, sliced about 30 angled fingers in the bottom and folded them toward the center to form the bevel that looks more authentic.

Step 4: Building the Head

My first thought was to create the head out of paper mache applied to a balloon, but I was unable to find the proper sized balloon to match the diameter of the body, so I decided on a ribbed design. This was similar to the way I made model airplane wings when I was a kid.

Unfortunately, I forgot to take a picture before I put on the paper mache, so you'll have to imagine what the ribbed cardboard looks like.

The downside of the ribbed method is that the ribs show through. so it is going to get several coats of wallboard joint compound to make it more spherical.

In hind sight, I should have spent more time looking for a balloon. The ribbed method never got perfectly spherical.

To give the paper mache more strength, I coated the inside with a layer of expanding foam.

Between the cardboard, hot glue, paper mache and a lot of wallboard joint compound, the head is getting rather heavy.

Step 5: Smoothing the Body and Adding Details

The body has now taken form, and is covered with the wallboard joint compound. I used a very wide strip of sandpaper attached to a piece of wood to make the body smooth and uniformly shaped. I spray painted the body white to seal the joint compound.

I found a drawing of R2D2's body detail, so I printed it out and attached it to the body so that I could make the appropriate marks where the boxes would go. I made a few masks for spray painting and covered up areas that were to remain white.

A sharpie and a straight edge were all i needed to draw the outlines.

Step 6: Spray Painting R2D2's Head

After getting R2D2's head smooth, I spray painted it a metallic silver. The spray paint is very silvery, but I later found that it's not as durable as other spray paints, even removable tape leaves a mark on it.

I laid out the design details and sprayed on the blue then carefully removed the tape when it was dry.

Step 7: Adding Details to R2D2's Head

R2D2's 'face' is a focal point, so I wanted to add some some carefully crafted pieces. R2's 'eye' is made from the lens from a dollar store plastic magnifying glass. In the movies, it always looks like a black void, so I spray painted the back side of the lens black and placed it into a recessed hole in it's frame. The frame is made from a scrap piece of MDF (Medium density Fiberboard). I like MDF since it cuts well and is easily smoothed.

The Red/Blue circle was made from a scrap of PVC pipe, and I attached a translucent piece of Plexiglas to the PVC. SO how does one make it blink?

At the dollar store I found a flashing LED gadget that contains 3 colored LEDs. I gutted the gadget for it's circuitry and installed it into the PVC tube. But since I only wanted red and blue, I removed the green LED and added another red LED in its place.

And finally the projector that R2D2 uses to project the memorable holographic image of princess Leia saying "Help me Obi Wan... You're our only hope"

Ok, so mine doesn't project anything, but I used a short piece of metal tube from a discarded vacuum cleaner and a fishing bobber painted gray.

Step 8: Attaching the Legs

Next step - attach legs. Since the little droid may end up in storage at some time, I wanted to make sure that I could easily assemble and disassemble it. I decided to make the legs removable, but sturdy enough to hold the load.

As I mentioned earlier, I glued some solid pieces of wood on the inside of the body, and the inside of the legs. This way, I can run a couple of long wood screws through the leg and into the body.

After the screws were in, I covered up the holes with a piece of decorative trim.

Step 9: Final Assembly

The head was designed to simply slide on the top of the body and it's ready to go

I was concerned that R2D2 would be a little top heavy and possibly fall over, but it appears that the large feet keep it steady.

Now all that's left to do is install a MP3 player with some amplified speakers and some appropriate sound effects.