With this simple connector you can chain-up all you Ultimaker robots. I have made it to stop the invasion at my desk by these little guys. Hanging on this chain even seems to make them happy (see the red one).

Each link has two ends where it can be connected to another one. There is also one start and one end piece to fix the chain on the wall with pins or small nails.

But I have to place a warning: this is not an easy print. There is a small revolute joint at the hook where the robot is fixed. When you print the connector two hot, this joint will become welded together and useless. I printed at the lowest temperature that was feasable. PLA at 185 to 200°C, depending on the filament. Layerhight was 0,1mm.