Chaos Engineer - T-shirt on RedShirtJeff.com
Like my last new shirt (It was DNS, I figured I'd mention my latest shirt design here on the blog in case you're interested:
As a parent of four, I thought it would be especially fitting on a onesie, therefore in addition to two 'normal' shirt options, there's a version for your baby (this version is out of print for now... let me know in the comments if you'd like to see it again!):