ON AND OFF THE AIR:
* Arsenio, meet Jonathon. That's the introduction happening at 11 o'clock tonight, as WNUV-Channel 54 debuts a new talk-show rival to WBFF-Channel 45's "Arsenio Hall Show" occupying the same time frame.
The new half-hour show is "Johnny B. . .On the Loose," and stars Jonathon Brandmeier, a Chicago radio deejay who has been trying for some time to translate his audio humor into a late-night television form.
Viewers may remember him from "Friday Night Videos," "Later. . .With Bob Costas" and from a one-shot NBC special last August. If memory serves, wasn't he also one of the many tryout guest hosts of the Fox network's "The Late Show" some season's back? (Everybody else was.)
So what is the show all about? We'll have to see, for publicity says, "there is no format for the show . . . basically, anything goes." But there are guests, and tonight's include actor Leslie Nielson (no doubt plugging his new movie, "The Naked Gun 2 1/2 ," and Oprah Winfrey.
* That's a neat gimmick NBC is launching tonight to showcase its excellent series "Quantum Leap." Have you seen the promos in which people verbally stumble as they try to quickly say, "It's Quantum Leap Week?"
Nightly episodes of the time-travel show starring Scott Bakula and Dean Stockwell begin with a two-hour special at 9 tonight (Channel 2) and include hour episodes at 10 p.m. through Friday.
* We are indebted to a "Sweathog"-influenced reader for this item relating to last week's trivia quiz in this space about the series "Head of the Class," in which Media Monitor invoked the memory of "Welcome Back Kotter," the 1975-79 series with Gabe Kaplan and John Travolta.
It turns out that if you have cable, you can still see the show. The USA Network screens it at 5:30 p.m. weekdays, 4:30 p.m. Saturdays and 5 p.m. Sundays.
* And speaking of cable reruns, TBS tomorrow has a special "June Brides" observance, showing wedding-related episodes of old series.
Beginning at 4:35 p.m., the shows include: "The Addams Family," "Laverne and Shirley," "Happy Days," "Bewitched," "The Andy Griffith Show," "The Jeffersons," "The Bob Newhart Show" and another "Andy Griffith Show."
* Also on cable but brand new is the latest world premiere film on the Lifetime basic service. "Death Dreams," with Christopher ("Superman") Reeve and Marg ("China Beach") Helgenberger can be seen at 9 tonight.
The stars play parents who suffer the tragedy of a drowned child, then are drawn into an exploration of the supernatural as the girl seems to reappear to her mother.