It's called a Deep Fake. Biden's face is being cgi'd onto an actor's body. The actor is real and wearing a face diaper. the computer images (Biden's face) can't react with the face diaper properly when it falls too low, causing the Biden image to stretch.

You can watch this happen over and over again for 2 minutes near the end of "Biden's" speech.

It's called a Deep Fake. Biden's face is being cgi'd onto an actor's body. The actor is wearing a mask and the computer images can't react with the mask properly when it falls too low, causing the Biden image to stretch.