Working in the IT industry, most people have similar hobbies[*]. Watching anime, playing RPGs, reading, programming, tinkering with hardware...
Once in a while, you talk to a colleague who leads some sort of 'double life'. During the day, they work their every day IT job, but they have a passion that is completely different.
Stefan Wimmer, one of the sysadmins at work, turned out to be a tango instructor. And not just some run-of-the-mill guy who tells you which steps to take when, no, he (and his wife Komala) get invited to instruct at tango schools all over the world! A few months back, he quit his job to devote all his time to the tango, which impressed me mightily.
What is the most unexpected hobby you ever discovered in a colleague?
[*]: Except the ones with small children (and I am at that age bracket where people have small children). Somehow, small children are a total time sink. ;)