Loads and loads of jugglers list "rubber chickens" in the lists of ker-azy things they can juggle, but none of the major juggling suppliers sell them. And why should they, I suppose, when they're so easy to build. I realize this is of rather specialized interest, so the instructions are after the jump...
The first thing you need, of course, are rubber chickens. I got three from Oriental Trading for about $8 a piece. (Oddly, they call it a "Realistic Chicken" when it's one of the fakest things I've ever seen.) Now, you could just juggle them right out of the box, but the floppiness of the neck means it's kinda hard to get the right spin on the chicken, and overall the chicken feels a bit light. So I wanted to stiffen up the neck and add some weight to the chicken.
I've seen juggling rubber chickens that had dowels (or possibly cut-up broomsticks) shoved down their throats, attached with staples. I knew I didn't want to staple the dowel in place, because the rubber always tore away from the staples in the ones I've seen. I did look at dowels at Home Depot -- but the wood felt like it was going to be a little hard (I've juggled axe handles, and I much prefer plastic) and maybe just a hair heavy. I ended up getting 1" diameter PVC pipe (8' for $2.50).
I measured the pipe by just sticking it down the throat of a chicken, until it just barely touched the chicken butt, and marking a spot inside the beak so the pipe wouldn't be very visible.
I then cut off that length of pipe, badly, with a regular hand saw and cut two more lengths of pipe to, more or less, match. (If you click through to an enlargement of the following picture, you can see how uneven my cuts were.)
I used the little sanding-drum bit for my Dremel to smooth out and round off the ends of the pipes. I then spent way too much time thinking about whether or not to glue the end of the pipe to the inside of the chicken butt. Doing so would help stiffen up the whole length of chicken, but it would also introduce a point of failure for the none-too-strong rubber. I decided that the sight of a rubber chicken with a hole ripped into its butt would be just too disturbing, so I decided to only glue the pipe to the neck.
As I approached the gluing stage, I realized that what had seemed like a perfect fit of 1" pipe down the chicken neck actually had some small amount of slack that would introduce wrinkles if I tried to glue the neck all the way around the pipe. Again after way too much though about the dynamics of juggling the chickens, I opted to glue the pipe to the neck along the 'spine' of the chicken. I dribbled GE Silicone II Household Glue down the neck of each chicken, inserted the pipe carefully in an effort to spread the glue along the pipe, and left them on their backs to dry over night.
I'm very satisfied with the results. The pipes provide just enough stiffness and weight to make the chickens very jugglable, but the legs still flop around comedically. Here's a very short video of Dr. Baron Ludwig von Evilschlager (well, me) juggling the chickens: