The term for such a grouping is a claque. In the 17th and 18th centuries, it was the province of the opera, where devotees would congregate at performances to huzzah or hiss their favorite performers. The custom largely died out in the late 19th century, but it had its roots in ancient Rome.
I dove into the history of the classical claque few years ago, when I wrote a glam rock play produced in Washington, D.C. by WSC/Avant Bard called Nero/Pseudo – with music by Jon Langford (Mekons, Waco Brothers) and Jim Elkington (The Zincs, Tweedy).
One of the most resonant stories of ancient times – with strange echoes in the afterlife of Elvis Presley – is the tale of a false Nero who rose up in Greece after the emperor’s suicide in 69 AD. This pretender resembled Nero and played the lyre, and he actually gathered a substantial mob of followers before he was intercepted and killed.