Accidentally spelled Lapses wrong....Oh well! My dyslexia got the better of me here it seems.
Bill angering thinking to himself: I thought the Fountain of Youth would stop him! Not make things worse! Why can't he give up already?!
Void calling out happily: Daddy, I found a crystal! Can I keep it?
Error answering Void nonchalantly as he reads: SuRe.
Mabel talking to Void excitedly: I'll help you! My sweater had pockets!
Null cooing at all the different crystals they found: Ooh~! They are so colorful! So pretty!
Error, not looking up from the paper in his hands notices Stan tugging on his coat: YES STaN?
Stan, blushing and still tugging on Error's coat: Error?
Stan gulps when he notices he has Error's attention: I got something for you...
Dipper, away from the group and watching Error and a younger Stan: Gruncle Ford, I thought Gruncle Stan lost his memories, with him only remembering the first 17 years of his life?
Ford, also watching Error and a younger Stan with unreadable eyes, answers Dipper: That's right. It's like we plucked 17 year old Stan and placed him here. But while memories are gone, feelings from within the SOUL stay...
Dipper notices Ford trailing off, now a bit worried something was wrong: Gruncle Ford?
Ford snaps out of it: Oh! It's nothing. Let's get the others.
This was just a little idea I may or may not write in the story later. Please remember that things in the story can change as it is not out just yet, especially as this picture is after Weirdmaggedon. Gravity Lapses is going to end differently then Gravity Falls, that much is for sure, but I'm not going to spoil anything there too much as it can change.
In this picture, Bill somehow either tricked or did something so that Stan got in contact with the Fountain of Youth that is in Gravity Falls. Bill wanted Stan to regress younger, that way he wouldn't remember meeting or falling in love with Error.
But the thing is that while Stan doesn't remember meeting Error, the feelings are still there. While his mind and body got younger, his SOUL didn't. So Stan feels certain emotions with people he doesn't remember.
Null, Void and Mable are not too worried here because they know and believe that everything is going to work out okay no matter the outcome. Null and Void especially believe that their Daddy will make things okay in the end no matter what. What Error is reading is a piece of paper with information on the Fountain of Youth, trying to understand just what is going on really and find the dang thing so they can get Ford some samples to study.
Dipper and Ford are more worried, as they fear this is not going to go away. Ford also has mixed feelings watching his now younger twin trying to woo Error, and also just seeing him so young. Stan is at a age before he was kicked out of the home by their Father.
Younger Stan is more brash, emotional and forward then Older Stan.
Still, in the end, Error is Error - said skeleton wonders just what is his life and why must these things happen to him. At least it wasn't one of the kids, he would kill someone if anything happens to them.
Bill knows this, and that is one reason he doesn't even try with Error's kids at this point. As this is after the series in this picture, the triangle dream demon knows by now just how over protective and deadly Error is. While this attracts him to the skeleton, he likes living thank you very much.
But I like to think that Bill makes plans to get ride of the competition for Error's love, only for it to backfire in multiple ways every single time.