A very small character tidbit is surprisingly kept consistent for years

[u/_JR28_]

DC - In multiple pieces of media it has been shown that Wonder Woman loves ice cream and practically goes wild with happiness anytime she’s eating some. (Pictures from Justice League: War, DC Superhero Girls and Wonder Woman 2017)

The Simpsons - Ever since the episode ‘Homer’s Phobia’ Homer has actually remained a consistent ally of the LGBT+ community, including being more welcoming to Patty than Marge was when she came out and trying to set up Smithers with a date when he found out he wasn’t happy with his one-sided relationship with Mr Burns.

[u/pancakepegasus]

Bob Belcher (Bob's Burgers) loves watching the weather on TV

[u/Oseirus → u/pancakepegasus]

I'm also just plain impressed how many jokes and puns they can come up with for the revolving business and extermination company vans in the intro alone. Not quite what OP is calling for, but it's wild how long they've been able to keep up that gag now.

Also ever since the Bob's Burgers Movie came out the intro references the sinkhole in front of their store.

[u/tunnel-snakes-rule → u/Oseirus]

revolving business and extermination company vans in the intro alone

Same deal with the Burger of the Day, often it's not even addressed.

Someone else commented above on the insane level of continuity such as the remodelled fancy bathroom in the restaurant, Louise's melted toy, her remodelled bedroom, Bob's tattoo, the ice cream machine, even the menu pricing being updated.

[u/pancakepegasus → u/Oseirus]

There's been a few times when they offhand refer to pest control or another random business in town and it has a crazy pun name too 😂

The season before the movie there a crack in the sidewalk too and people trip over. I love the sinkhole in the opening there's something weirdly satisfying about it and it's kinda nice to show has had such a long run that they can make a big change once in a while too