Kerbal Space Program

You can create Bills indefinitely with the help of two pods joined with a docking port.

Steps to Replicate:

1) Start a new Sandbox game.
2) Make a vessel that is just 2 Mk1 pods attached with 2 docking port jr.'s at their tops.
3) Have Engineer Bill be in the 2nd/top pod (no one needs to be in 1st/bottom pod).
4) Launch vehicle.
5) Detach docking ports.
6) Switch to pod with Bill in it unless it's already in control.
5) Wiggle the vehicle with the movement keys until it is on the launch pad beside the bottom pod.
7) Target the other pod's docking port jr by double clicking it.
6) EVA Bill.
7) Switch to Construction Mode (Click hook icon on right panel).
8) Click on the other pod's docking port jr. and just move it a little and place it with another click.
9) Board craft.

You will observe that Bill has entered the craft but his double has also spawned on the craft.

Duplicate Bill some more:

10) Roll or spin craft ('q' or 'e' works) until the impostor double flies off.
11) EVA Bill.
12) Board craft.

We have another double (without even doing any further construction mode).

Repeate steps 10-12 to summon Bill's double indefinitely.

Notable features: If you switch to a duplicate, you cannot control him (hence why we had to fling them off the pod). If you right-click them, they are named Bill Kerman, but if you switch to them, their lower right display name is "Crewmember name here". Also, right-clicking the real Bill shows he has a thrust limiter and other vessel-related properties.

This is obviously KSP's way of saying "Happy Halloween!" (But as seasonally apt as this is, please do fix this.)