On The Weekend Watch:
A SERIES MILESTONE -- Although originally dismissed as a weak spinoff from "The Cosby Show," NBC's "A Different World" reaches the 100th episode plateau tonight (at 8:30, Channel 2). In the milestone episode, Hillman College (where "Cosby" daughter Denise (Lisa Bonet) matriculated before returning to the parent show) is in the path of a forecast hurricane. Dawnn Lewis, Cree Summer, Darryl Bell and Jasmine Guy star.
A SERIES PREMIERE -- As the early ax falls on some low-rated series (such as NBC's "Man for the People" and "Pacific Station," both going into hiatus after Oct. 27), a new series is also premiering Friday, on baseball-preoccupied CBS. It's "Palace Guard," making a movie-length debut (at 9 p.m., Channel 11) before taking up a regular 10 p.m. Friday slot. D.W. Moffett and Marcy Walker star in a romantic mystery set against the backdrop of international hotels.
WATCH THE SKIES! -- There is something irresistible about the notion that alien visitors are keeping their eyes upon us (or whatever it is they use as sensory organs) -- and perhaps studying some of us more closely. In "Sightings: The UFO Report," a Fox special on Friday (9 p.m., Channel 45), people who claim to have been abducted by visitors share their experiences.
UP INTO THE ANDES -- Imagine a train journey that carries you repeatedly around precipitous bends and across perilous bridges over great gorges. The dizzying trip in the high Andes of South America is featured in a repeat Saturday of "Great Railway Journeys of the World" (at 9 p.m. on Maryland Public Television).
THE SPORTS SCENE -- The "1991 World Series" gets under way this weekend on CBS, with Jack Buck and Tim McCarver calling the action from the Minnesota Twins' home park, the Twindome. Games one and two are scheduled at 8 p.m. Saturday and Sunday (Channel 11). And note that some early baseball programming Saturday (also Channel 11) includes "Road to the World Series" at 2:30 p.m. and "World Series Greatest Moments" at 3:30 p.m.
THE MOVIE MARQUEE -- Some quirky contributions from the big screen in the coming days. At 11 p.m. Thursday on MPT, for example, is "Jimi Hendrix," a documentary about the incandescent guitarist who once smashed his instrument to smithereens on stage and called it music. At 10 p.m. Saturday on Channel 54 is "Strangers on a Train," the 1951 Hitchcock classic that inspired the more recent "Throw Momma From the Train." (Trivia note: The mother in the original movie was played by character actress Marion Lorne, who later would be Aunt Clara on "Bewitched.") And at 9 p.m. Sunday is the made-for-TV reunion "I Still Dream of Jeannie," with Barbara Eden and Bill Daily returning from the 1965-70 series.