The Opera Company of Philadelphia, already known for its "Random Acts of Culture," surprised the lunchtime crowd at Geno's Steaks in South Philadelphia Saturday with a "pop-up performance" of the "Anvil Chorus" from Verdi's Il trovatore.

Two years ago the group achieved internet fame with their "flash" performance of "Libiamo ne' lieti calici" ("Brindisi") in the aisles at Reading Terminal Market. Customers joined in on the famed drinking song from Verdi's La traviata and the video went viral. It currently has over three-and-a-half million views on YouTube.

Later that fall, the Opera Company teamed up with over 650 choristers from 28 participating organizations - accompanied by the Wanamaker Organ - to perform the Hallelujah Chorus from Handel's "Messiah" at Macy's in Center City. That YouTube video is now approaching EIGHT million views.

All the "pop-up performances" (they don't like to use the word "flash mob") are funded by the John S. and James L. Knight Foundation's Random Acts of Culture program.