I have some personal habits that I can attribute directly to others.
One is that I almost always have a writing implement or three (ideally, a couple of pencils, a ballpoint pen for carbon forms, and a pen for regular writing) atop my keyboard. I rarely use anything other than IBM Model M's, so there's considerable space. I picked this up from a high school/university friend who used to do the same. Of course, lately, I've had my Space Pen take over both pen roles. It's not nasty to write with, although it could be better, and it does a lovely job on carbon forms.
Lately I've discovered a habit of saying "doo doo dooo" etc under my breath (and sometimes not under) when I'm doing sort of mindless things, or else thinking intensely about something (so everything else is sort of disconnected). I blame one of "my" grad students for this - he does the same thing. When I asked him about it, he said he finds it annoys people less than whistling. I never whistle though.
I emailed a prof recently to tell him I've taken his habit of saying "thanks much". He claimed he didn't remember where he first picked it up. I assume it's a leftover of learning English as a second language, but I could be wrong. I'd never heard it before, although there's a few others around the department who I've caught saying it as well.