As part of the dialog that launches the Yard Sale, Lisa and Homer have this exchange:

Lisa: So, this is our season finale – a fourth wall joke?! Aren’t there any characters or quests?
Homer: Well, I guess you could make Lovejoy ride his train for the finale – that kind of fits.

Why exactly does it fit? Because the last episode of season 24, premiering in the US on Sunday, 19 May, is called “Dangers on a Train“. Here’s the trailer from the ANIMATION on FOX Channel on YouTube:

Note: Homer also suggests that we make Carl celebrate his Icelandic heritage, and you can see why here.