Same word as jokiest:

batty, campy, crazy, daffy, dippy, flaky, fooling around, foolish, for grins, freaky, gagged up, goofy, idiotic, illogical, inane, incongruous, irrational, jokey, joshing, laughable, loony, ludicrous, nonsensical, nutty, off the wall, preposterous, sappy, screwy, silly,