Ok, so Käfer is the only place to go after the rest of the tents are closed.  The Paulaner Beer is served 90 minutes later at Käfer than anywhere else on the Wiesn Oktoberfest grounds. 

The 1,900 outdoor seats start filling up after “last call” is announced at other beer tents.  The 1,000 seats inside are usually reserved.  So the really drunk and really dedicated end up finishing their night outside—where soup is served to keep you warm on those brisk nights.

This means that while the smart people in town are in bed and passed out by midnight, the true beer drinkers continue their festivities at Käfer until 1:00 a.m.  There are many Oktoberfest patrons that can blame their morning hangovers on Käfer, Paulaner Beer, and the California Sun band.

Käfer is known as the most 'upscale' tent at Oktoberfest. Its meals are significantly more expensive (and better quality) although the waiters are notorious for the upsell...don't fall into the trap of getting the 200 euro duck. It's not fun.