Bill and Dipper get set up on a date by their siblings. Both 18.
Gravity falls park
"Got your sister?" Will Bill's little brother said incognito meeting Mabel who was also incognito both dressed in a brown suit, glasses and hat.
"Yeah your big bro here too?" Mabel asked checking her wristwatch.
"Yeah here in 5 minutes she ready to go on this date?" Will asked Mabel.
"Yes but she has no idea just like Bill." Mabel shook Will's hand both going their separate ways.
Five minutes later
"Mabel! Where are you?" Dipper yelled looking around for her sister. "If she wasn't showing up then why tell me to come here?" Dipper asked herself.
"Probably the same reason Will told me to come here." Bill said taking a seat on the bench next to Dipper "Names Bill Cipher." He said.
"Dipper Pines." Dipper introduced shaking his hand "So your sibling told you to come to this bench at this time too?" She asked.
"Yeah to play chess but he's not here." Bill told her.
"Mabel told me we were gonna explore the park." Dipper said then her eyes widened "Wait you like chess." She asked happy.
"Yeah!" Bill said excited as well "And you like exploring like me?" Dipper nods making both smile.
"Wow so were both sorta nerds." Both said then laughed "We both said the same thing! We did it again!" Both said again laughing harder.
"This is crazy!" Dipper said looking at her feet "We already have a connection!" She said twiddling with her thumbs.
"Hey." Bill said taking hand looking in her eyes "Do you wanna talk a walk and see where it goes?" He suggested and Dipper nodded blushing a little seeing their hands together as they walked away hand in hand.
"It worked!" Mabel said and high fived Will since both were watching the encounter of their siblings.
"Who knows maybe one day well be in laws?" Will said making Mabel gasp and start to dance around with Will at the idea.