What is Scenery-Chewing

[Catlady (Rita Prince Winston)]

"Shewing the scenery" is what used to be said of an actor who was 
really hamming it up and being over-the-top nrealistically 
overdramatic. There was a time (1800s IIRC) when audiences LOVED 
that. Styles change. Maybe the phrase began as a reference to King 
Lear's mad scene and the actor having such fun pretending to 
be a loony that he tried to eat the (fake) shrubbery.