This was discovered in the comments of a "not constructive" question on Stack Overflow. Further exploration got me to this page.
$ curl -LH "Accept: text/bibliography; style=bibtex" http://dx.doi.org/10.1136/bmj.313.7072.1659
Will return (whitespace liberally added):
@article{Craddock_1996,
title={Introducing Selfcite 2.0--career enhancing software},
volume={313},