TITLE: Examples of math hoaxes/interesting jokes published on April Fool's day?
QUESTION [111 upvotes]: What are examples of math hoaxes/interesting jokes published on April Fool's day?
For a start P=NP.
Added 2022-04-01 Anything new in 2022?

REPLY [4 votes]: A genuinely natural information measure [arXiv:2103.16662]

The theoretical measuring of information was famously initiated by
Shannon in his mathematical theory of communication, in which he
proposed a now widely used quantity, the entropy, measured in bits.
Yet, in the same paper, Shannon also chose to measure the information
in continuous systems in nats, which differ from bits by the use of
the natural rather than the binary logarithm.      We point out that
there is nothing natural about the choice of logarithm basis, rather
it is arbitrary. We remedy this problematic state of affairs by
proposing a genuinely natural measure of information, which we dub
gnats. We show that gnats have many advantages in information theory,
and propose to adopt the underlying methodology throughout science,
arts and everyday life.