We have a super-mario-brothers tag that seems like it would be used for questions about the Super Mario Bros. series.
However, this tag is not used just for that specific series within the Mario franchise: There's a question about Super Mario Galaxy on it, which, while part of the greater Mario franchise, is definitely not a Super Mario Bros. game — it is completely different gameplay and location-wise from the 2D Super Mario Bros games, other than the general characters. There are questions, such as this one, which are not specific to the small group of Super Mario Bros. games.
This tag should be renamed to super-mario or mario-franchise, as its current name and tag description are a lot narrower than its actual use is.