They remind me of John Langdon’s ambigrams, calligraphic creations that have extremely clever rotational or mirror symmetry.

Here’s an interview with him, and a whole magazine (Ambigram) with articles, galleries, and automatic generators.

Some handcrafted stop-motion type:

from a roundup of Creative typography art.

I also dig Dave Bollinger’s letter-packing test, and a similar Processing sketch.