Editing: Is it possible to change a part of a subject in the video in premiere pro?

Hi, 

I would like to know if it is possible to change a part of a subject in a video in premiere pro or in any other video editing program?
What  I mean is: 

For example I have a video of a walking cat. Is it possible to cut off the tale of the cat in the video. So viewers see a walking cat without a tale when they are watching the video?

Or is it possible to change the colour of the tale of the cat, so viewers will suddenly see a cat with a pink tale?

Or things like this? 
If it is not possible, I would like to know does this technique exists? Is it anywhere possible in some kind of video editing program? Thanks in advance!