In the Rugrats episode "The Sky is Falling!", when the world is just about to "END", Angelica herds the babies into her "Fall-in Shelter." First of all, the sign was so neatly (and professionally) printed (neither Stu nor Chas did it-they were playing tennis at the time); when Angelica makes more signs in the series, it's just a bunch of scribbles. Second, note the words. At one point, "shelter" was spelled "Sheltel".