When he was head of one network or another, Fred Silverman would laugh off one of his garbagey programs by saying, "Well, it's not going to win a Peabody," the way apologists for trash often say, "Well, it's not Shakespeare." It isn't terribly hard to imagine NBC Chairman Grant Tinker being cornered at a cocktail party these days and coming up with the same sort of line.

He could say, "Well, it's not 'Hill Street Blues.' " Or maybe, "Well, it's not 'Taxi'--we canceled that one, you know."

If one were to watch only the promos on NBC these days, and take note of what's being sold and how, one might think he had flashed back to ABC circa 1975 and been caught in a kitsch warp. What people ask about "Manimal," the NBC series premiering at 8:30 tonight on Channel 4, is "Is it as stupid as it sounds?" and the answer is "No, but stupid enough."

And when it's added to all the other cartoonish escapism offered in prime time on NBC and the other networks this year, it all gets to be suffocatingly excessive. It's like being nibbled to death by Smurfs.

For what it is--and what it is it probably should not be--"Manimal" is fairly well done, not so childish that an adult couldn't tolerate it during a weak hour, and even produced with a twinge, just a pinch, just an eencey-weencey trace, of wit. Prof. Jonathan Chase (Simon MacCorkindale, of "Death on the Nile" and other films), psychologist and criminologist, has the ability to turn himself into the animal of his choice at will in order to remain on the trail of no-goods and miscreants and catch them at their no-good miscreancy.

His colleagues include a woman police detective (Melody Anderson) and the by-now traditional black flunky (Michael D. Roberts), described by NBC publicity as "a hip, loyal friend he met while serving in Vietnam." There is a flashback to their days in Vietnam, when the professor first perfected his "transmutation" trick, and a lucky thing for him, or for Glen A. Larson, who produced this silly show and many others like it.

On the premiere, Prof. Manimal turns himself into a hawk to survey a big nerve gas caper, and also becomes an owl, a panther and a pussycat. The panther seems to be his specialty. Only one on-screen transformation is shown (a la "The Howling" and other such films) because those makeup tricks don't come cheap, and TV shows try to.

When he is teaching his class, one girl whispers to a friend of the dashing professor that he has "eyes like a hawk and ears like a bull elephant; I hope everything else is equally sensitive." Later, during a bedroom scene involving a crook and a hooker, the man says, "You're in for the night of your life" and the woman says, "Nothing kinky, okay?" This they would not have said on a prime-time kiddy show on ABC in 1975, but it's hard to twist that fact into anything remotely resembling a sign of progress.