From the Medlabs level, you are turned into a Strogg in a comfortable fashion! See full description for details of the process.

The process (from QuakeWiki):
0:20 - Transfer is scanned by lasers.
0:50 - Transfer is injected with steroid dosage and accompanying nanite colony via cardiopulmonary system.
1:03 - Transfer undergoes facial mutilation by a Strogg Scientist.
1:40 - Transfer's legs are removed cutting directly though the femoral arteries with a dirty saw blade.
2:23 - Mechanical legs are placed where the transfer's legs used to be. Then metal plates are riveted to the arms and body, and the legs are attached to the transfer's stumps.
3:15 - Neurocyte is implanted into the cerebrum using a large hypodermic needle; the subject almost immediately gains knowledge of the Strogg language.
3:30 (unseen) - Metal plates and armor are attached to the subject's backside, including the body and the back of the head.
3:40 - Transfer is put in a tank and transported to the Registration Station.
3:55 (interrupted)…