This site claims to be "the first anti-Mormonism site in Japanese". They suggest households put up a sticker on the door to ward off those callers. The Mormon on the sticker is of course a "character" and so the organization helpfully supplies a backstory (キャラクター紹介) for ニーファイ君 where he has just arrived in Japan feeling and is ripe for being told to sling his hook.