Okay, so... it states the name of the sword guy (Exor) is based off Excalibur (further implying the connection between the Mushroom World and Earth is intra-dimensional cuz why else would an inhabitant of the Mushroom World be named after something on Earth if travel between the two was scarce?) but Mario doesn't get the reference because swords don't exist in the Mushroom World... well, they clearly do, because Exor's there. I'd say swords are just very uncommon in the Mushroom World and non-existent in the Mushroom Kingdom (at least up until this point). Crisis averted...