Quick and easy Super Skrull.
I used the Avengers series Skrull figure, did the heat & pop method to remove the arms. Then I cut and carved/grooved/reshaped the forearms from a 5 inch movie series Mr Fantastic figure, and attached them into the forearm holes. These arms were bendy, so no need to recreate the elbow joints here.
A little carving and detail painting on the arms to make them fit and look like they were stretching out from under the uniform, and here we have the Super Skrull.

Thanks for looking!
-Ant