I think if I worked with someone who asked me why I couldn't be "normal" and buy a car like everyone else, I'd be hard put not to laugh out loud. I think the last time someone gave me that particular line, I was 13 years old!

I might ask the co-worker why they care so much. Or, depending on the day, I might stop and say "wow. Had a junior-high-school flashback there. I could have sworn you just tried to peer-pressure me. Weird. So, how about them [insert random sports team]?" and make it very clear that I was not going to even recognise that as having any bearing on me whatsoever.

I've had a supervisor get bent out of shape about my biking, but I'd already demonstrated that public transit wasn't reliable enough (due to road construction and route changes that happened after I got the job) and I told my supervisor straight out that unless I got a substantial raise, there was no way I could or would consider purchasing, insuring, and maintaining a vehicle.