"You have Comedians in Cars Getting Coffee. James Corden has Carpool Karaoke. What's next in lazy car-based, non-comedy?" Galifianakis asks.
He also attacks Seinfeld's Bee Movie and suggests, "Don't you think it should have been called D-Movie?"
Showing some fight, Seinfeld fires back, "Do you think if they only made one Hangover and didn't make the other two it would be considered a comedy classic? Do you think that you destroyed what would have been a comedy classic by the cash grab of 2 and 3?"
There's a quick Seinfeld reunion when Wayne Knight aka Newman walks on set and then Galifianakis gleefully welcomes Cardi B to the show.
"The most important thing is that you're relevant," he says to her in yet another dig at Seinfeld.
Watch the full episode below: