2 Answers

No it is not possible unless your playing splitscreen but other than that no, sorry.

Single-Player
Single-player mode in the "Call of Duty" games features an action-packed storyline. It allows for one person to play through the single-player portion of the game.

Split-Screen Multiplayer
Split-screen multiplayer mode allows up to four players to play on the same PlayStation 3 console and one television screen simultaneously.

Online Multiplayer
Online multiplayer allows one player to play online against others from all over the world. Only one person can play online multiplayer on a single PlayStation 3 console. "Call of Duty" does not support split-screen online multiplayer.

Read more: Can Two Players Play "Call of Duty" Online From the Same PS3? | eHow.com http://www.ehow.com/facts_6939804_can-duty_-online-same-ps3_.html#ixzz21TJLmxtH