I’ve recently discovered that both Ubuntu and Debian projects provide a single mirror to use if you put your hands on an outdated server with a discontinued release.

For Ubuntu you should use: http://old-releases.ubuntu.com/ubuntu/
For Debian you should use: http://archive.debian.org/debian/

With these mirror you should be able to deboostrap an old ancient Debian buzz (1.1) or Ubuntu Warty Warthog (4.10) :)