You have no idea how long I've wanted to put THAT down, have you?
Alrighty. Here's the gist of it..Warning: Spoilers included about Turbo's backstory, though if you've read on him, you should know most of it.
First off.. The most known 'possible' last names are Rnos, Renos and Runnerup. In a way, all three of them are correct.
Considering the amount of times I've used Turbo OUTSIDE of Roleplaying, it is not unlikely to see variations on his last name appear.. But I'll go and explain them all.
Runnerup, first and foremost, is his actual last name. There, I said it. His name is Turbo Runnerup.
Rnos is a bad joke.. Doing it correctly, it would actually be TurboR NOS.. The R being Turbo's last name, Runnerup... NOS.. is basically turbo. 'Nitrous Oxide Systems'.. Nitro, Nitrous, NOS, Turbo, whatever you name it, it's the stuff that makes cars go faster. This 'last name' is used for email purposes, and ALSO my Billy VS Snakeman 'last name' for Turbo.
Renos is a last name BASED on Rnos, obviously enough. I first used it for my Guild Wars characters, make them look like one happy family. However, in using it, I gained the idea to ACTUALLY use it.
To put it bluntly, Turbo's actual name is Turbo Renos. Turbo was found by his adoptive father, who took the first name off of the clothing Turbo was wearing as a baby, and gave Turbo his own last name- Runnerup.
Considering Turbo himself doesn't know of the original 'Renos' last name, and wont find out for awhile, Turbo is officially called Runnerup for his last name.
Really, you have NO IDEA how long I've wanted to do this part, even though Turbo originally had NO last name, and that the Renos part is only what, a year old?..