Are you using Dolphin with a Wiimmfi Unbanner NAND, if so then that's why.
Yeesh, some people are just so eager to cheat in public lobbies. I mean, other than Wiimm having a bit of a stick about people making fun of a Certain Part of his country's history (rather a small sticking point, honestly; that rule only gets you a slap on the wrist, not like the permaban for
cheating - not like he hurls sexist abuse at a guy who draws Star Wars characters with big breasts

), the rules are perfectly reasonable. And it's not like he's asking you to pay!
You could try to detect it by putting code into the game, which tries to find behavior that is different between a real console and an emulator.
There are some small, unique differences between how things are handled in all four of the formats (Wii, vWii, Wii VC, and Dolphin) that can be used to detect which one you're running on.
Necroposting on a three years old thread, congratulations!
Mac and serials can be forged easily, trust me...
Yeah, they're hardcoded into the network devices, but the computers those devices are connected to can make them lie.
but yeah you should only megabump like that if you have an actual question to ask