Yeah, except for, like, a futuristic, laser, arm cannon. / Maybe some magical creature or...paranormal thingem took it.
Is this a generic gag or a Gravity Falls-esque hint? Michael Rianda, one of the writers of Gravity Falls, hosted a Reddit chat in which he said it was a generic gag. But he also made some questionable statements, and he is not Alex Hirsch. I don't know on this one.
standing with one foot on top of something - Robbie, Pacifica, Nathaniel
Robbie, Pacifica, and Nathaniel Northwest's statue have all been shown in this episode and the previous one to stand with one foot on top of something in the same pose, at a moment where they are asserting their pride and authority. It's an odd possible coincidence. Note that Stan was seen standing in the same pose in Headhunters.
heart pops / We have a winner!
This may have been just a fun gag, but I wrote it down anyway. When Dipper sees Robbie and Wendy going out, the heart balloon pops behind him. And when Dipper wins the toss and gets the platypus for Wendy (at least I think it's a platypus), Manly Dan is in the background playing the old strength-testing game of pounding a hammer, and seeing how high you can get the lights to light up. He obviously won.
By Trembley!
This is an expression used by the pioneers Dipper and Mabel meet. It's an obvious reference to the previous episode, where the kids meet ex-President Quentin Trembley.
baby with bandaid on chin
The pioneers' baby has a band-aid on his chin. There are two points I want to make about that. First, band-aids had not been invented yet. Second, some people think this baby was named Fiddleford H. McGucket. I think that's nuts because even though McGucket is old, he's not 150 years old.
Stan looks out his door
The kids run past the Mystery Shack in winter, and a younger Stan looks out the door. We see the banner in the background for the Royal Order of the Holy Mackerel. A popular theory is that this is actually Stanley, Stanford's secret twin brother. Personally, I think it is Stanley. Check out this page to see why.
Fertillia's descendants / Blendin's ancestors unknown
Who are Fertillia's descendants and Blendin's ancestors? Ever wonder why Blendin was sent to this time and place instead of someone else from the Time Anomaly Removal Crew? See above for the theory about Fertillia's descendant, Old Man McGucket.
Wait...why does it smell so bad in here?
You're not guilt tripping me, Mabel. Not this time.
Mabel has guilt tripped Dipper before.
Not H.G. Wells approved
H.G. Wells was a sci-fi writer from the 19th and 20th centuries who coined the phrase "time machine".
