Marty tracks down where elderly Edna Strickland lives, and brings back her missing shoe, holding it aloft for her to see from the upstairs flat window. A woman walks by and stares at Marty quizzically as he does this; he just responds with a shrug before she leaves.
Marty is trying to convince a 17-year-old Emmett, who works at the courthouse and pretends he has no interest in science, to tell him about the rocket powered drill that old Doc told him he was working on at the time. When you click "Don't worry, I'm a scientist too":
1931 Emmett: [sarcastic] So tell me something, Mr. Scientist, from your vast storehouse of scientific knowledge!
Marty: Uh, the legbone's connected to the... thighbone?
At a certain point you can ask Doc about Kid Tannen. He explains that Kid will be serving a life sentence in prison in the near future within 1931. This conversation prompts:
Marty: Wait, if Biff will be born in 1938 and Kid will be in prison...
Doc: As I recall, he escaped in 1937 for about three hours.
Marty: That's a busy three hours.
Doc: No kidding.
At the same time, Marty expresses concern that telling Doc's younger self about the equation's solution might screw up the time stream.
When examining the 1931 Newspaper in the inventory which changes from Doc being killed on the courthouse steps to being killed on a paddywagon, Marty's comment will most likely echo the gamers' comment.
Marty: Now that's just not fair!
Just this suggestion of a plan to save Doc from his death:
The sequence where Emmett and Edna trade insults while Doc rescues Einstein from the courthouse roof.
When Doc disguises Marty as a 1930s mobster, he tells him that the fake mustache is essential to not being recognized, and that he is easy to disguise with his "nondescript features". The lingering look of disappointment on Marty's face when Doc says this is good for a laugh. Along with him muttering "nondescript...?"
This is referenced later in the same episode, if you ask Zane to draw a caricature of Marty. He comments that it doesn't really look like him, and Zane replies that "there wasn't much to work with".
Made funnier by the fact that Marty's face is anything but "non-descript".
Episode 3: Citizen Brown
At the start of the episode, Marty has crashed the DeLorean into a billboard after Doc has been erased from the timeline. Marty decides to clear something up if you click on him:
Early on, Citizen Brown is strapped to a wheeled bench right in front of a giant speaker while Edna and a guard look on. Marty plugs his guitar into the speaker, then jumps down onto the bench dramatically intending to play a loud chord and blast himself clean out the door with Brown. He hits the strings... and only moves a few inches, completely subverting the awesomeness of the maneuver.
Marty: Okay, that was a little less dramatic than I'd expected.
Marty informs Doc that his alias at the moment is Carl Sagan.
When talking to William McFly about who would know about what Hill Valley is and why it was erased from existence, he suggests asking "Scary Mary" — aka old Edna/"Mary Pickford" — but then warns that she's basically an insane hermit. Marty then comes out with this:
Marty: I think she'll talk to me. [very, very awkwardly] I'm pretty good with...women...
[cue Doc shaking his head in dismay]
At the very end, Doc and Marty are dumbfounded by Edna ending up with Kid Tannen.
Future Marty: Bring [Marty] along too! This concerns all of us!
Marty: What do you mean? Does somethin' happen to us?
Doc: Do we turn into assholes or something?
Heck, this whole scene is a hilarious parody of Part I's ending. Three Martys, with three DeLoreans, from three alternate futures show up, and immediately start bickering over which one of their timelines is the most important, and which one Doc should be helping - all voiced by MICHAELJ. FOX, no less! Doc and Present Marty's reactions? They leave in their own time machine.
If you examine the mop:
Marty: The top of a mop. I can flop it on a cop. I can swap it for a top. I can...I think I'll stop.
When refreshing Old Edna's memory of what happened, there are various prompts you have to give, various questions to answer - and there are, as usual for the genre, several wrong guesses included. But when the time comes to remind her of the villainous saloon owner's last name, the only option is Tannen.
.