It may be obvious, but had a fun use for clipping masks. I created a new top level "Dirty" layer of grey smudges.
In the puppet I put "Create Clipping Mask" on the "Dirty" layer.
I guess you could say she was Triggered!
(I mean I could put a trigger on the Dirty layer to make it appear... but I ended up just using a separate puppet as making changes to existing puppets can move the origin, requiring all previous recordings of the puppet in scenes to be repositioned.)