Well, you know how this works. Ask your deep burning questions about the world's most famous plumbers and their games. I will answer any question that is appropriate. Go!

Ok... I will give you a few questions to test you... I pretty much already know the answers.

1) What is the so called "Minus World" in Super Mario Bros.? And where can I find it?

2) Are there any other Nintendo characters apart from any Super Mario characters that make cameos in any of the games?

3) What is Super Mario Bros. The Lost Levels?

And finally...

4) IS the princess in another castle!?!?!

1: The Minus World is a glitch in the game. By passing through a wall near World 1-2's exit (due to said glitch) it is possible to get to "World -1," also known as the "Minus World," which is considered by the game to be "World 36." It is the same as World 2-2 and World 7-2, but the warp pipe at the end takes [the player] back to the start of the level.

2: Yes. I'm not quite sure if you want examples, but here's one: in Mario and Luigi: Superstar Saga (GBA) the Psyko Kamek, in Little Fungitown, is wearing a robe from a White Mage from the Final Fantasy series.

3: This was the release of the original Super Mario Bros. 2 (Japan only) to the rest of the world. The "Super Mario Bros. 2" that was outside of Japan was actually another game, Doki Doki Panic, with the sprites switched to those of Mario and co. because they felt the real Super Mario Bros. 2 was too hard for other gamers and would make them lose interest in the series.

4: Yes. I think...

LOL I like the answer to number 4 : D . Nice, I think you know Super Mario Bros well enough.