Let us not forget the immortal
“oo ee oo aa aa, ting, tang, walla walla bing bang”
Ross Bagdasarian was a lyrical genius, I tell you! Genius!
Which he did really wunderbar! 
Jock-a-mo
AKAIK, it only appears in one song.
First thing that came to mind was “Bismillah! No, we will not let you go!” from Bohemian Rhapsody.
The Association’s tongue-twisting Along Comes Mary manages to shove tribulations, masquerade, flaccid, and psychodramas in its rapid-fire lyrics in under three minutes. . . and then ruins the (pretentious) effect with the hook line “When we met I was sure out to lunch.”
So did John Prine. Example lyrics:
Hold it! Stop it! No! No! No! No!
Bang! went the pistol.
Crash! went the window.
Ouch! went the son of a gun.
Onomatopoeia
I don’t wanna see ya
Speaking in a foreign tongue.
Workshop of the Telescopes by Blue Oyster Cult has a few:
By Silverfish Imperetrix whose incorrupted eye
Sees through the charms of doctors and their wives
By Salamander Drake and the power that was undine
Rise to claim Saturn, ring and sky
By those who see with their eyes closed
You’ll know me by my black telescope
Nick Cave & The Bad Seeds’ “We Call Upon the Author to Explain” includes words such as ‘prolix’, ‘myxomatoid’, ‘jejune’, ‘cabal’, whose obscurity is of course somewhat the point…
My last suggestion was voided by the “no proper nouns” restriction, so, drawing on US Top 40 hits, I nominate 1953s “I Want a Hippopotamus for Christmas” by Gayla Peevey.
Other words in the song include “ignoramus.”
I guess I’m pretty much an outlier in the fact that I recognized all the songs when I watched the Linda Rondstat version back when it came out.