Syphon Filter: Dark Mirror Easter Egg - UMD in episode 2, part 4

In the in-game cutscene at the end of episode 2, part 4 - "Freeman's Answer" the optical disk in Gabe Logan's hand is a UMD (Universal Media Disk), the exclusive disk format of the PSP (the relevence being that Syphon Filter: Dark Mirror is a PSP game on a UMD).