Once there was an internetworking protocol named DECnet, which like IP used 32-bit addressing. When the time came to support Ethernet and similar LANs in DECnet Phase IV, the mapping of DECnet node addresses to 48-bit Ethernet MAC (hardware interface) addresses was solved by changing the MAC address in software to be the same as the DECnet address! (DEC did set the "locally administered" bit in all such MAC addresses.)
When the programmer responsible was located and asked "Why didn't you use ARP?", the IP protocol for dynamically mapping IP addresses to MAC addresses, he simply replied "What's ARP?"