Strictly speaking, Mario and Luigi aren't cartoon characters. They're video game characters. They have appeared in cartoons, though, and so we'll include them. If we didn't, we wouldn't be able to show you this great picture.
Although everything about the picture screams 'staged,' we believe that it's authentic. These are just two guys working on a job somewhere, and they didn't walk out of the house intending to look like the most famous fictional plumbers of all time. What are the chances of that?