The season 2 finale is a rare and often overlooked gem in tv series - and a prime example of constantly breaking the 4th wall while still staying on-topic.
Picking up the cues from previous episodes, the mysterious diner-chef hears his train arriving, making him pack his stuff and leave the diner for good - but he and the whole cast soon find themselves trapped inside the diner when fire breaks out. And toxic waste. And a mudslide.
When Kubiak eats all the food and Jerry fails to fix the air ventilation system, there is only so much "airtime" left ("so to speak").
To add insult to injury, the dangerous shape-shifting master criminal "Chameleon" escaped prison and currently hides inside the diner.