When my little brother was a teenager, he and his buddies used to use deliberate spoonerisms to disguise "forbidden" words. E.g., they would say, "I need to pake a tiss," I have to crake a tap," etc. One time, though, they didn't think it through and the deliberate spoonerism came out "I have to shake a tit."

This particular one was said to my brother's buddy's very prim and proper mother, who was not amused.

Arjay