Even though Andy Serkis has done lots of regular acting on stage and in movies, he is best known for his motion capture performances, and especially so on account of his roles as Caesar in "Planet Of The Apes" and Gollum in "The Lord Of The Rings" and "The Hobbit".
Here he is on Stephen Colbert's show, where it is not only demonstrated by way of stock footage how the motion capture technique works, but where Andy assumes his Gollum persona again in order to read Donald Trump's tweets.
It's hilarious, check it out!