Philip Bratt is PewDiePie's friend from Sweden who played with him in the beginning of the channel. Together they played games like Amnesia and Penumbra. He also appeared in webcam by PewDiePie's side.
He has a channel called "Philip Bratt".
Beside this, he has a video with PewDiePie entitled "EPIC PEWDIEPIE - BEHIND THE SCENES! :3" which shows Felix on the PC listening to a Strokes song: The End Has No End, while Philip records him from a bed; Then it turns into a short part of a Amnesia gameplay.
You can watch the video in here: https://www.youtube.com/watch?v=s-C1HWceTPE
It is believed that Philip was probably the first video editor on PewDiePie's channel.