Characters
I used to be with 'it', but then they changed what 'it' was. Now what I'm with isn't 'it' anymore and what's 'it' seems weird and scary.
— Grandpa · The Simpsons

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Grandpa complains that the world moved on without him. What was once understood as cool has been redefined, leaving him behind. Playing with the word 'it' makes his confusion both funny and a little sad.
Context reviewed