Kerbal Space Program

I've just done some testing of this and the reported behavior is confirmed. I didn't stop at setting kerbal mass to 100kg; I set it in the multi ton range. First to 50 tons and then 500000 tons. 50 tons is sufficient to noticeably affect TWR, in some cases enough to prevent launch entirely. (simple craft; pod, tank, engine. Or pod, SRB). Setting it to 500000 tons is easily outside the mass that a vessel's joints can support and it will immediately collapse on the launch pad, demolishing the vehicle and killing the crew. (the point of setting it that high was merely for demonstration purposes)

Testing was done in a stock environment, aside from changing kerbal mass.