American Express paid for a 5 minutes "Seinfeld" web episode advertisement featuring Jerry as Jerry and Superman doing "Nothing" around New York, hanging out like they were buddies.
You'll need flash to view the content but it's not in cartoon flash. It's an actual video. You probably already know that Superman was featured in every Seinfeld episodes in some way or another. So this is no surprise.
If you don't have flash or don't want to give your email to American Express...
Windows Media Player
http://www.jerry.digisle.tv/media/Uniform_LAN_IV_LAN.wmv
Quicktime
http://www.jerry.digisle.tv/uniform_lan_quicktime.html