IPv6 addresses in the form of
862A:7373:3386:BF1F:8D77:D3D2:220F:D7E0 are much harder to memorize or even transcribe than the 4 octets of IPv4.
Is there an intentionally-weak hashing function which could be reversed to find that the phrase, say, "This is relatively benign and easy to spot if the phrase is bent so as to be not worth paying" would hash to a target IPv6 address? The hash would, of course, have many colliding inputs to choose from, and a potentially more memorable sentence, such as this example phrase, could be automatically offered.
I guess there are two parts: First a weak hash with good distribution in both directions. Second is an algorithm for selecting memorable phrases from among the many collisions (short, consisting of words from a specified language, perhaps even following a simplified grammar).
Although the hash function would need to be weak, I don't doubt that the effort is still significant - however, once the phrase is known, the computation of the hash to the target address is very quick.
I found this related idea, Piphilology, for memorizing some digits of π:
How I wish a drink, alcoholic of course, after the heavy lectures involving quantum mechanics!