Steven Roselle shows Maya 2020’s Original Geometry Input functionality, applying deformers to a posed rig.
It used to be that certain situations required you to disconnect a rig to apply deformers. You can quickly find out why by applying a deformer to a posed character to fix some stretching issues. Things go bad quickly.
Original Geometry Input.
However, with Maya 2020, there is new functionality with deformers that allow you to apply them ad-hoc. Original Geometry Input attributes in the deformer let you use things like a Delta Mush to posed characters. Autodesk Steven Roselle walks through how it works.