I think Martin would totally be having that same sleeping position Marty has. And that Jennifer would find out about this after the first night in George's hideout like the next morning and be like:
Jennifer: Is this normal for him?
George: (waking up from that same awkward sleeping position) What do you mean?
Jennifer: Nevermind.
And later on in 1931 when she happens to find with find Doc both Marty and Martin passed out/deep asleep.
Jennifer: Huh.
Doc: Apparently that's just a universal constant for Marty.
Further on, I also think this would've 100% happened at some point:
Marty: (sees how Martin sleeps) Is this really how I look like when I sleep?
Jennifer: Yeah, you absolutely look like a looser.
Martin: (sees how Marty sleeps) Is this really how I look like when I sleep?
Jennifer: Nooo, pretty baby! You're too cute to look like this!
Doc: (is present in the background for both and shakes his head)
Bonus round: Marty finds out about Martin decking Griff.
Marty: (to Jennifer) Okay, I know you're not my girlfriend. You're actually just her from a different timeline, but what do you actually SEE in him? (points at Martin)
Martin: (Is happily stimming with his rubber band collection + some fidget spinners from 2016)
Jennifer: Oh, he punched Griff.
Marty: ...what?! (has 2015 Griff flashbacks) You mean Griff Tannen?? As in Griff from the future???
Jennifer: (has THAT look on her face) Oh yeah~ whacked him unconscious with a keyboard over the head~
Marty: (pointing at Martin again) Wait, THIS guy did it???
Martin: (is now patiently and innocently watching a butterfly land on his fingers)
Jennifer: Yepp.
Marty: (dread) Heavy.
CTM AU Dialogue/Scene script: Finding George in 2016
They're going down into the sewers here.
CONTEXT - KB has agreed to bring Martin and Jennifer to George so they can also have a safe place to hide from the police in Hill Valley in 2016.
OUTSIDE - OPENING TO THE HILL VALLEY SEWAGE SYSTEM -NIGHTTIME
Martin and Jennifer look in disgust at the sewage flowing out of the opening, while KB pulls something out of their backpack.
Martin: Are you sure my dad is somewhere in here?
KB: Of course he is! Do you know how terrible the Internet and Phone reception is down there?
Jennifer: (holding her nose) Well, the reception for guests certainly is.
KB: Exactly!
KB manages to pull out a pair of yellow raincoats along with 2 LED flashlights and hands them to Jennifer and Martin.
KB: (Claps) Time to meet Georgie.(Grinning) Don't worry! The clowns have been well fed.
Martin and Jennifer exchange an uncertain glance.
INSIDE - HILL VALLEY SEWAGE SYSTEM - TUNNELS
Martin, KB and Jennifer carefully wade their way through the waste, while lighting their way ahead in the darkness.
KB: His hideout very deeply hidden, so it might take a while to get there.
Martin: KB? How do you know my dad anyways?
KB: He's my video editor.
Martin: No, I mean - How did you get to know him in the first place?
KB: (hesitates, the actual reason is more personal) You see, he still needed a technician. Someone to help him to set up a safe and untraceable access to the Internet. I happened to know a thing or two about it.
Jennifer: Couldn't he have just done that by himself?
KB: Not without becoming a Citizen Plus.
Martin and Jennifer shudder at that thought. The implications of that are clear. The trio approaches a corner with a soft light being emitted just behind it. They turn off their LED flashlights.
KB: We're there.
INSIDE - HILL VALLEY SEWAGE SYSTEM - GEORGE'S HIDEOUT
The trio enters a large cavernous area, where the floor seems to be a mix of both orderly industrial steel floor grids and a mess of cables going above and below it all, connected to electrical Equipment monitors hanging from the walls, illuminating the area instead of light bulbs. There are makeshift furniture, made out of trash and disposed off scratched parts. It's not much and it doesn't seem orderly, but is enough to make living here bearable, and the arrangement of the furniture is clearly divided by function and purpose. A basic cooking and eating area with provisions here, a sanitary corner with a portable shower and cleaning products there and a sleeping area with a patched up hammock and cushions within a short dead end tunnel.
KB: Mr. McFly, I'm back! I got you some refreshments. (Walks over to the eating area) It's mostly just Algea Cake and fill up Algea Shakes again. But I've snatched some Peanut-brittles and Cornflakes as well!
As KB says this, Martin and Jennifer make their way up some industrial stairs, which lead to an area above the one they've just entered. A singular large monitor illuminates the area, at the center of it sits the silhouette of an old thin man, George McFly. He's analyzing the video file KB has given him last night, zooming in and enhancing at every frame that shows the Delorean. Trying to catch a glimpse of the faces of who is sitting inside. Jennifer is in awe at the size and quality of the video in front of her, as well as the amount of the editing Equipment George has in front of himself alone. Martin meanwhile stares at George and wants to speak up, but shame keeps him from breaking the silence. KB rushes the stairs up after Martin and Jennifer.
KB: By the way, I got you some visitors.
George: Not now, KB. (is so focused he doesn't even turn around to take a look) How often do I have to tell you to not bring people down here?
KB: I know, but-
George: I know you mean well, however, I'm not getting any younger packing and moving everything around again. I can't just keep on-
Martin: Dad?
George stops whatever he was doing and slowly turns in his chair towards Martin. He looks like as if he's seeing ghost. Martin interprets this as the worst possible case and can't even bare to look at his father. It's his fault after all that George is down here all by himself.
Martin: I-I know you're probably upset with me. A-and disappointed. You've got every right to be-
But before Martin can say another word, George stands up and wordlessly pulls his long lost son into a tight hug. Shocked Martin stands still. Not sure what to do next he looks at Jennifer and KB for help before awkwardly returning his father's hug. George starts to sob. There are no words able to express the magnitude of this moment for George.
George: (whisper) You're home.
Jennifer watches the whole interaction with a sense of guilt, yet a small pang of jealousy. (Her meeting with her Citizen Plus father didn't go as well.)
