Spelling Entertainment is hot under the collar over a “Beverly Hills, 90210″ spoof that aired on TriStar TV’s “The Edge,” and has fired off a letter to the studio demanding a public apology.Both shows air on Fox Broadcasting Co., one reason cited by Spelling attorneys in their missive to the Sony Pictures Entertainment division. The letter called the sketch “completely tasteless” and “crude,” alleging that it implied acts of incest between characters on the hit teen drama. Spelling has threatened a trademark infringement lawsuit against TriStar unless it issues an apology and promises not to air the program again, noting that the use of the “90210″ trademark was particularly disturbing because the shows air on the same “network.” Neither Spelling nor TriStar officials could be reached, but TriStar reportedly responded that the routine was obviously a parody and an exaggeration. The company is also said to have pointed out its commitment to free expression, to the point of skewering “Designing Women”–which is produced by sister Sony unit Columbia Pictures TV–on “The Edge’s” pilot episode. “The Edge” has drawn respectable ratings as part of Fox’s Saturday lineup and features an ensemble led by Julie Brown. David Mirkin is the exec producer.