A year after its release, you may have thought there wasn't a ghost of a chance of any fixes being made to Ghostbusters. But Terminal Reality is going to give Xbox 360 players a reason to start busting ghosts in multiplayer again, with a patch that fixes glitches in the multiplayer Achievements. That means that, following the update, you should be able to get the "Egon's Guinea Pig" Achievement! Tell your mood slime -- it'll be thrilled!
You'll just ... have to wait a little longer. According to the announcement on TR's Facebook page, the patch is "currently awaiting approval for distribution, which is likely to coincide with the Xbox 360 firmware update this Fall."