Fast Track Sallies

My favorite euphemism for diarrhea is "fast track sallies," as in; "I can't have caffeine because it gives me the fast track sallies." I have no idea where the saying comes from. It's not something that was used in my family when I was growing up - I've read it somewhere and decided I liked it, so now I use it. If anyone has any info on the origins of this saying, I'd love to find out about it. I did an internet search, but didn't come up with anything. Thanks, Katherine