終末何してますか？忙しいですか？救ってもらっていいですか？ has an "English" title on it's Japanese cover beside the Japanese one "Do you have what THE END? Are you busy? Shall you save XXX?". I'm guessing the author did it themselves. The capitalisation on THE END is presumably supposed to reflect on 終末 (shuumatsu - the end [often used for apocalypses etc]) punning on 週末 (shuumatsu - weekend) and the XXX is because the Japanese title gets to omit the subject and English can't.

Needless to say, the official English translations didn't keep that title, going with "What are you doing at the end of the world? Are you busy? Will you save us?"