Insulin and bodybuilding?

I've been a (type 1, love my life) diabetic for 25 years and only recently discovered that apparently some bodybuilders use insulin for muscle growth. This is hilarious to me because of how difficult being a diabetic makes exercise (I exercise every day and I'm well used to it myself).

What effect does insulin have on bodybuilding, do users take before/during/after exercise? I'm fascinated by this. Can nondiabetics get hypos from insulin injections?