Shell star variables. Pleione and Gamma Cassiopeiae itself are both variable stars that have intermittent shell episodes where strong shell features appear in the spectrum and the brightness increases or decreases significantly. At other times the shell is not detectable in the spectrum, and even the emission lines may disappear. Shell star A shell star is a star having a spectrum that shows extremely broad absorption lines, plus some very narrow absorption lines. They typically also show some emission lines, usually from the Balmer series but occasionally of other lines. The broad absorption lines are due to rapid rotation of the photosphere,
A Star Is Burns play in the opening moments of the episode is a parody of "U Can't Touch This" by MC Hammer. The opening of Bart's film "The Eternal Struggle" is a reference to The Amazing Criswell's narration in "Plan 9 from Outer Space". Barney's film contains references to "Koyaanisqatsi", and the music of the film, which was composed by Philip Glass. Barney's film also features musical selections from the aria "Un bel di vedremo" from Act II, pt. 1 of Puccini's opera "Madama Butterfly". In its original broadcast, "A Star Is Burns" finished 57th in the ratings for the week of February