I've seen that professional character animators will often adopt gestures and expressions from the voice actors, and apply them to their characters. Using this same principle: is it OK for demoreel purposes to take an actor's scene from a movie, and animate your character following the actor's performance? Obviously, it would be better to create a completely new character with his/her own story and animate their emotions from scratch. I want to animate a character for my demo reel, but I'm getting stuck on coming up with a storyline etc and just want to get into the learning curve of animating a character. Here's another example: what if I created a chicken and got her to act out a line of Shakespeare- borrowing the gestures from a screen actor?
Another point along a similar line: Say I wanted to animate a cat character and I video taped a real one jumping in the air. Am I cheating if I bring the mov up on my screen and copy the timing into my animation- ie "OK, at 2.5 secs, his leg is here and his head is angled like this..."