Eric Grundhauser writes In 1975, a Cat Co-Authored a Physics Paper:
Jack H. Hetherington was a professor of physics at Michigan State University in 1975, when he finished what would become an influential and often-cited physics paper. The academic writing, entitled Two-, Three-, and Four-Atom Exchange Effects in bcc 3He, was an in-depth exploration of atomic behavior at different temperatures. It would have flown over the heads of most lay people, not to mention cats.
He was all set to send it to Physical Review Letters, which today describes itself as “the world’s premier physics letter journal.” However, before he dispatched it, Hetherington gave the paper to a colleague to get one last set of eyes on the piece. This is when he ran into a strange problem. Hetherington had used the royal “we” throughout the paper. As his colleague pointed out, Physical Review Letters generally only published papers using plural pronouns and adjectives like “we” and “our” if the paper had multiple authors.
Hetherington [later] wrote that after giving the issue “an evening’s thought,” he decided the paper was so good that it required rapid publishing. Unwilling to go back and replace the plural voice in the document, he did the next best thing and just added a second author: his Siamese cat, Chester. Of course just listing “Chester” as a co-author probably wouldn’t fly, so he invented the name F.D.C. Willard. The “F.D.C.” stood for “Felix Domesticus, Chester.” Willard had been the name of Chester’s father.