Viz productions uses the wrong spelling for the name of Inuyasha's sword in the show Inuyasha. The way they spell it is Tetsusaiga, but the "tsu" in the middle can be used in 2 ways. The way they use it when writing the kanji for it is as a glottal stop, a brief pause between syllables. It sounds almost like a slur of the previous letter, and is therefore romanized as a double letter, being spelled as 'Tessaiga' instead of 'Tetsusaiga'.

That's my useless information for the day lol.