Definitely the gimme. Either a slingshot around the sun or the Guardian of Forever would bring the USS Enterprise crew to Gotham. You've probably seen the fan-made YouTube video where Kirk and Spock mix it up with Batman, Robin and The Joker.
"S" as in "splendid", "M" as in "marvelous". Batman '66 was played straight - for laughs. Get Smart was Mel Brooks' parody of the Bond spy craze. A craze that included Derek Flint, Matt Helm, The Man From UNCLE, The Girl From UNCLE and I Spy, just to name a few. This would be epic!