The Python community has a long history of April Fool's postings to news:comp.lang.python (a.k.a. mailto:firstname.lastname@example.org). We've collected references to a number of them here. If you know of more, please update the page.
Postings and Press Releases
2003 Stackless Perl 4.0
2004 'goto' for Python (which actually works!)
April Fool's PEPs