質問: It appears that the character is limited to Katakana. Is the character used in writing Hiragana and Kanji?
回答: You're right that it is normally used in katakana, but it can sometimes be used in hiragana words, as a point of emphasis, to lengthen a sound more than it normally would be: うぜー かわいいー なのだー You can add it to い adjectives. Otherwise, the word in question is generally written out in hiragana rather than in kanji, but it is apparently alright to add it directly to a kanji for emphasis or silliness: 長いー 大きいー 怖いー 馬ー鹿ー!