I recently noticed that the phrase “we were merely freshmen” from that song by The Verve Pipe has almost entirely ’e’s for vowels (it took me a while to notice the ‘y’, so I originally thought it was exclusive). This suggests a new category of interesting phrases, that only contain one kind of vowel.
We can differentiate between phrases caught in the wild (actually published somehow), and phrases that are reasonable enough that one could imagine them being spoken or written. If we allow for unreasonable phrases (and only require correct syntax), then they could be arbitrarily and trivially long.
I’ll start it off by searching the works of Shakespeare (as found here). In the first scene of The Two Gentlemen of Verona we have the character Speed speaking the line
The shepherd seeks the sheep, and not the sheep the shepherd; but I seek my master, and my master seeks not me; therefore, I am no sheep.
The first phrase is five words long, six if you count the name “Speed” preceding the line. This ought to be beatable. Clearly Shakespeare was only an amateur.