On the BBC TV series Monty Python's Flying Circus the phrase "And Now for Something Completely Different" was more than just a snappy catch phrase, it was, and still is, one of the finest examples of segue humor (no, not a joke about the Segway human transporter). John Cleese's deadpan delivery was absolutely crucial, including his perfectly straight face and the slight pause between "something" and "completely". One can easily find sound clips on the web of John Cleese saying this famous line.
Needless to say, the phrase itself is the exact antithesis to a good segue, serving only to highlight a (deliberately) incoherent juncture, rather than hiding it or smoothing it over.
Many contemporary attempts at segue humor do not even come close to the sheer simplicity of this single phrase. For example, around 1998 Conan O'Brien had a sketch involving a guy named Segue Sam on his Late Night show. Segue Sam would help Conan bridge the most ridiculous transitions between topics (and usually die in the process). However, the Segue Sam skits were long and arguably at most moderately funny, and while the intrinsic humor of the phrase "And Now for Something Completely Different" is debatable, at least it had the merits of succinctness and simplicity.
By now, many North American standup comedians seem to have no concept of a comedic segue at all, except perhaps for "Hey, did you guys ever notice how", which isn't even intended to be humorous.