All the people who watched "Welcome Back, Kotter" in order to see Gabe Kaplan would fit on the head of a pin. And you'd still have room for the James Watt fan club. Kaplan seems to be entertaining some outer-space delusions about his appeal and prowess as a comic performer; he has put himself front and center in "Lewis and Clark," the new NBC sitcom premiering at 8:30 tonight on Channel 4, and as a result, the show comes off as a void within a void.

Kaplan plays restless Long Islander Stewart Lewis, who moves to tiny Luckenbach, Tex., with his carping wife and crabby kid because he wants to run a country-western nightclub. He also wants to smoke cigars and talk to the audience the way George Burns did during the inventive lulls of "The Burns and Allen Show," but George even puffed funnier than the expressionless, sluggish Kaplan.

Guich Koock plays Gomer-Pyle-ish country boy Roscoe Clark, who imparts all kinds of homespun wisdom to Kaplan; in the premiere, Kaplan fires him for no reason and then rehires him for no reason. One fears that in television, we are not going through an age of reason.

As a gabby bartender, Michael McManus gets to make with colloquial similes we doubt ever got colloq'd, such as "grinnin' like a dead hog in sunshine." As in "Kotter," the role of the star's wife, here played by Ilene Graff, is mainly that of straight woman, although Graff does get to utter what may be the show's high point of scintillating wit when she refers to dinner as "wham, Spam, thank you, ma'am." Ahem.