Atari's XE Game System was a dud commercially like the previous 7800 video game system – but what a brilliant dud it was!
For all intents and purposes, XEGS was a console version of Atari's 68XE computer. Unlike 5200, which was also identical to an Atari 8-bit computer, XE Game System was a true hybrid and compatible with all of Atari's 8-bit computer hardware and software.
The system looks like a games console and acts like one until a keyboard is attached. This triggers a boot that is identical to XE computers. Other peripherals included a CX40 joystick and a XG-1 light gun. Atari sold XEGS in two sets: the basic one came with just one joystick; the deluxe one with a keyboard, joystick and light gun.
As a fun detail, XEGS would start up Missile Command when it was in console mode and no cartridge was inserted. Nice built-in bonus, if there ever was one!