I loved that on the back of Lisa's L'il Eco-Warrior magazine was an ad for the Canyonero Hybrid. Hah !! Quite a stretch back for that reference. And then over the end credits, you see Lisa reading the last issue of Eco-Warrior magazine.
Tupac hologram: "Why won't you people let me die ?"
Lisa: "I thought your name was 'Kidzrule'.
Dr. Kidzrule: "It's short for 'Kidzrulevich', which is Romanian for kill all the children."
The Lobster tank is back -- at least none were floating on the surface.
Those synchronized swimmers made up to look like Artie Ziff .... were just a little creepy.
Nelson: "Her smile makes me feel full, like I actually ate dinner last night."
Bart: "If you never eat, how come you're so fat ?"
Nelson: "Americans can be fat and poor -- that's what makes us so great."
I liked that one of the robot versions of Marge was Bender from Futurama.
In addition, there was slot machine Margebot, clothes washer Margebot, two Margebots with eye-patches for some reason, spider Margebot, Slinky pushme-pullyou Margebot, and let's not forget the Margeketeers who evolved wings and flew away (because life finds a way, which is a Jurassic Park reference).
Totally agree with @Galileo908 -- whoever is doing Martin Prince's voice now needs to go back to voice acting class -- because his voice sounds way off, sounds more like Rod/Todd Flanders.
We even got a Gov. Mary Bailey sighting.
All I could think of when Lisa had her smile was the image of Lisa on The Log from 'Lisa the Tree Hugger' back in Season 12. I wonder where that Log is now.