If a smile doesn't spring to your lips the moment you hit play, check your vital signs immediately. In Best of the Muppet Show, the three latest installments to debut on DVD, our furry friends, along with guest stars Steve Martin, Carol Burnett, and Gilda Radner, remind us that this really is ''the most sensational, inspirational, celebrational, Muppetational'' show. On top of the always clever antics of Kermit and his puppet posse, you've got rats dancing the cancan, pigs dressed as Eskimos crooning ''The Lullaby of Broadway,'' and the Flying Zucchini Brothers bursting out of cannons -- rendering the spectacle all the more ''Muppet''-tastic. EXTRAS An introduction by creator Jim Henson's son Brian offers a few fun facts about each segment (such as that the writers won their first Emmy for the Burnett episode); otherwise, an early drawing of Beaker from 1977 is as exciting as it gets. But the treat of seeing Gilda again makes this DVD a first-rate pleasure.