Actually, it *is* a Sun engineer joke. The 10 Mbps predecessor was a chip called the "Big MAC Ethernet" -- in this case, it was a mere pun, since MAC stands for Media Access Control, i.e. the Ethernet data-link layer. When they designed the 10/100Mbps chip later on, they decided to turn the pun into a full-out joke, and they called it the "Happy Meal Ethernet."
On a Solaris machine, the interfaces are named by the driver type, so instead of "eth0" you'll see something like "hme0" instead.