For a period in 2000-2001, back when I was learning how programming languages work, I wrote up a few simple languages in the vein of Befunge and Brainfuck — essentially elaborate jokes that explored areas of the design space that other, wiser folks had avoided. I sent descriptions to the esolang mailing list, where similarly bewildered people hung out. I expected a giggle at best.

12 years later, I’m still getting emails. I guess there are a lot of other weirdos on the Internet!

• HQ9+: the first tutorial-complete programming language.
• 4DL: the first explicitly four-dimensional programming language.
• Beatnik: an interpretive (but not necessarily interpreted) programming language using free-verse poetry and the Scrabble scoring system.

Around the same time, I wrote my first Forth implementation (for the 68000). Whether Forth qualifies as either an esoteric programming language, or an elaborate joke, is in the eye of the beholder.