It is possible to connect the Sony Playstation Portable handheld game system to the Sony PlayStation 2 console by way of a USB cable. The PS2 recognizes the PSP as an external device. Very few games for either system take advantage of this function.
It is fairly simple to connect the Sony PSP to the PS2 by way of a standard micro-USB to USB cable. However, once connected, there is not much that can be done with them. Some games that are capable of interfacing to transfer data and unlock bonus content are "Metal Gear Solid 3: Subsistence" with "Metal Gear Acid 2," the two versions of "WWE SmackDown! vs. Raw 2006" and "SOCOM: Fireteam Bravo" with "SOCOM 3." This has a lot to do with the PSP's 2005 release and the PS3 superseding the PS2 the following year; the PS3 has much greater functionality with the PSP.