Now Do Classical Gas is a quote from The Simpsons character Lenny in the episode ?Last Exit to Springfield.? In the scene, Lenny asks Lisa, who is playing acoustic guitar, to play the piece ?Classical Gas? by Mason Williams. The scene became the subject of YouTube Poop remix videos popular on the Facebook page Simpsons Shitposting in early 2017.
Definition #2 for "now do classical gas"
"Classical Gas" is an instrumental musical piece composed and originally performed by Mason Williams. rdf.freebase.com