Dipper is 16 and Bill is still a demon. Dress is melody's.
Las Vegas wedding chapel

"Yo you may now kiss that bride in dress cause iz tradition." The weird Elvis pope said and then Soos and Melody kissed "And Boom your married! next couple!"

Later

"So Soos remind me why las Vegas and not a fairytale dream castle?" Mabel asked the groom. They were in the reception room.

"Because that guy is like super funny and an honor to see 'the' Elvis especially at my wedding and times are tuff." Soos replied.

"Oh Soos." Mabel shook her head "I could've turned your wedding into something far better for free!" She said swinging her juice around "But keep this juice always keep this juice!" She said like she's drunk.

"Uh Soos let's go to motel it's getting late." Melody said taking Soos by the arm and kissed him.

"Now there goes a happy couple." Dipper said smiling wide feeling giddy "Now Mabel you know I'm not always into this but..." She started "But whatever I got wedding fever!" She hugged Mabel.

"Dipper." Mabel said looking serious "You and I are going to binge watch Every wedding show on TV and talk all night cause its time for... SISTER BONDING!" She screamed happy.

"Let's go like right now!" Dipper said then sipped her juice "Man I'm loving this juice!" She yelled her and Mabel running to their motel room conveniently next door.

"Great now I gotta deal with 'Bill when are we getting married?' And 'if we aren't getting married I'm going to avoid you!' And junk "Bill said to himself "And did someone buzz this juice?"

"That was me." The Elvis impersonator said "Gotta keep the job interesting."