After passing behind the giant Mara facade and then turning back under the bug room, the car appears to "stall" for a moment and you can hear rats squeaking and chirping. Then, you race around the corner and a cloud of mist is sprayed (not unlike the effect of the waterfall in Pirates of the Caribbean) and a tree branch with rats crawling on it is projected onto the mist.
Like I said, as far as I know it works. The cloud just never had enough time to completely reform, and it's not as striking as the ride's other effects.
It's difficult to film, but you can get an idea of the placement in this video from 10:15 to 10:30.
In Japan's, it's replaced with the smoke ring scene, which is in this video at 2:14.