Camera Cropping / Overlay Tool?

[OtterPaw]

Is there anyway of being able to crop a portion of cam video so you can use it to overlay onto images?

for example, cropping your mouth so you can overlay it onto something like a potato to make a talking potato.

 

[WizardCM]

You can manually crop by holding Alt and dragging edges inwards. You could also use a Mask filter with an image to do the same but with a fade around the edges for example. I'd probably also use the Color Correction filter's Opacity option to help blend it into the item behind it.