Music Jason Alexander on the moment he realized Seinfeld’s ‘George Costanza’ was based on Larry David Apr 20, 2019 Facebook Twitter Pinterest WhatsApp Linkedin ReddIt Email Print Seinfeld’s George Costanza character was originally based on Seinfeld co-creator Larry David but is surnamed after Jerry Seinfeld’s real-life New York friend, Mike Costanza. Here’s that moment where actor Jason Alexander realized this.