Portal 2 introduces a cast of memorable characters that enrich the narrative and contribute to the unique charm of the game. Chell, the silent protagonist, returns from the first game, navigating through the Aperture Science facility and facing new challenges. Wheatley, a personality core with good intentions but limited intelligence, becomes an unexpected companion to Chell. The witty and sarcastic GLaDOS also makes a comeback, bringing her trademark dark humor and an evolving relationship with Chell.

The cooperative multiplayer mode introduces Atlas and P-Body, two robots with distinct personalities and characteristics. Players control these characters, each equipped with their own portal device, and collaborate to solve puzzles. The banter and interactions between these characters inject humor and camaraderie into the gameplay, creating a multiplayer experience that complements the solo narrative of Portal 2.