The actor brought the character to life via motion capture in director Peter Jackson's films and admits he went "pretty method" when it came to retaining the character's physicality.
"I used to walk on all fours off set when we were filming 'Lord of the Rings'," Serkis explains. "I spent a lot of time in preparation for that. I would go off for walks on all fours for hours. I did occasionally come into contact with other people, so I just had to pretend I was looking for something."
The Brit tells NME.com he's glad the "Lord of the Rings" role came later on in his life, as he wouldn't have been able to cope with the level of fame that came with the films if he was younger.
"I was in my late 30s when it exploded," he explains. "I'm grateful it happened when it did. It was an extraordinary time; so many things came out of that experience and whether I like it or not that role lives with me on a daily basis. It will never go away."
Serkis will reunite with his "Lord of the Rings" castmates for a series of online chats with Stephen Colbert to help raise money for cinemas struggling due to COVID-19. Elijah Wood, Sean Astin, Cate Blanchett, Orlando Bloom, Billy Boyd, Peter Jackson, Ian McKellen, Dominic Monaghan, Viggo Mortensen and Liv Tyler are all expected to join the virtual get-together.