The riddle
What Do You Call a Fish Wearing a Bow Tie?
Swapping the middle
Sophisticated has five syllables, so-phis-ti-ca-ted, and sofishticated keeps all five. The main change is in the second one, from "fis" to "fish". Wiktionary dates the first English use of sophisticated to about 1601, from Medieval Latin sophisticatus. It gives the American pronunciation as /sə.ˈfɪ.stə.ˌkeɪ̯.dɪd/, so the change is a single consonant, s to sh. The first syllable is a little different too, since the joke says "so" and the dictionary says a short uh sound.
A word that once meant impure
The word has changed meaning. Wiktionary lists an obsolete sense, mixed with a foreign or inferior substance and so not genuine or pure, and the modern senses of worldly-wise, cultured and refined. It also gives complicated, when speaking of technology. The refined sense is the one a bow tie is meant to suggest.
Where the bow tie came from
Wikipedia traces the bow tie to the 17th century, when a scarf tied around the neck to hold a shirt closed was taken up by the upper classes of France under the name cravat, from the French word for Croat. Sizes of fixed-length bow ties run roughly 14 to 19 inches around. A modern bow tie is tied with the common shoelace knot, which is why that knot is also called the bow knot.
Making more fish words
A group can try to build fish words of their own by replacing a sound in a longer word. The test is that the replaced sound must still leave a word listeners recognize. Another quick one: what has a head but no brain.