In the preview for the upcoming April 24th episode, 'The Gilmore Girls' makes a reference to '24' when Lorelei goes shopping for a new car with Luke. It turns out to be such an unpleasant experience, that she suggests that Jack Bauer should torture terrorists by taking them car-shopping with their exes.
But that's cool; it's not a Zonk. '24' is definitely set in an alternate universe. It has to be since they've gone through at least four presidents since it debuted and nuked Valencia, California, early in this season.
The jury's still out on 'Gilmore Girls', what with all the references made to it by other TV shows (and because of its own propensity for making references to TV shows that should be sharing the same TV universe it inhabits - like 'The Donna Reed Show'). But as I mentioned earlier in regards to 'Supernatural', there is a splainin for the references to 'Gilmore Girls' on other shows - there is a TV show based on life in 'Stars Hollow' in the TV Universe.
But even if it is in another TV dimension, it doesn't have to be the same one that houses '24'. Thanks to 'Sliders', there are thousands of alternate dimensions to choose from!