Polyglot written in 7 esoteric programming languages: Malbolge, Brainfuck, Whitespace, Spoon, asdf, 123 and EXCON. It pretends to be a program in the language whose interpreter is working now :)
If you want to know how it was impemented please read wiki: en, ru. This link shows appropriate source view. How it should look in fact:
All sources licensed under MIT license except asdf, 123 and EXCON interpreters.