What a coincidence, I just wrote my explanation of Luigi's full name in another post that I did...
Luigi's full name is:
Luigi Q. Cwunchy III 
My boyfriend thought of the name "Luigi" and I just thought it was perfect for my little dog. Then, we remembered this episode from The Chipmunks where Alvin, Simon, and Theodore named their puppy "Cookie Chomper III." I originally was going to name Luigi, "Crunchy," but people thought that was kinda weird and gross (haha..I THINK IT'S CUTE!) and so I changed it to "Cwunchy" (the way a baby or little kid would say it..to kinda make it sound nicer heh), and then added the "III" for no reason (kinda taking off the Chipmunks episode)...I definitely have never had a Luigi Q. Cwunchy I or II before! haha. And then randomly picked a letter of the alphabet.... "Q." .....which means nothing
The name fits him just right and I love seeing the reactions people have when I tell them his whole name
It's usually..."WHAT THE HECK??"