This oneshot is a crossover with three of my favorite childhood shows, in case you can't tell there are other pairings in here.
Ben 10 X
Foster's Home for Imaginary Friends X Gravity Falls X Transformers Prime.

Four brunettes, and one raven haired teen, sat around an old rickety wooden table.
The kitchen inside the Mystery Shack was silent as the Four teens, and the one tweenager, sat in silence.
The five boys had become friends over the first month of summer; or so Dipper Pines had told them.
"Guys, we're friends. I think, right?" He sat awkwardly at the table as the other four young men.
Ben Tennyson sat on one side of the table, fiddling with the strange black wristwatch he never took off.
Mac McFaust sat across from Dipper, he pulled his phone from his backpack and shot someone a text,
before turning his attention back to Dipper's question.

"Uh, yeah. I think so. I mean, I haven't exactly been good at making, uh, actual friends."
He scratched the back of his neck sheepishly. A snort drew their attention to the raven haired teen, known as Jackson Darby.
"We've only known each other for about two months, Mac. We're almost to the friendship stage, but that requires
trust building exercises." He shrugged, slumping in his seat. "Or so I've been told by teen magazines, and crappy after-school specials." Mac fidgeted in his seat for a moment, a strange look passed over his face. "We can tell each other a secret, something we'd trust friends with.
Guy friends, actually." Jack raised an eyebrow, then shrugged. "Ah, what the heck. What deep dark secret do you wanna know?"
Dipper slammed his hands on the table, glaring at the teen. "Is it true that you're in town with Aliens!?"
Jack snorted, leaning back in his chair. "Aliens? What gave you that idea?" Dipper Pines procured a magazine,
showing a familiar looking yellow Chevrolet. Jack swore mentally, then folded his arms. "I plead the fifth."
Dipper sighed, stowing the magazine back in his vest. "Worth a try." He glanced over at Ben, who was giving Jack a strange look.
"Ben?" His eyes met Dipper's and he raised an eyebrow. "My Grandpa is a plumber, my Mom is a fitness guru, and my Dad is an office drone.
No big secrets, promise." He said, fiddling with the watch again. Dipper frowned, but gave up on his line of questioning.
He didn't bother questioning Mac, he had seen the creatures he had ridden into town with. These: 'Imaginary Friends', that he worked with.

"Well..." It was Mac who piped up.
"I came up with the idea, so why don't I start?" He sighed, nervously glancing away. "I've got..." He screwed his eyes shut.
"A crush on a woman fourteen years older than me." Dipper snickered, an eyebrow raised. "That's your secret?" Mac glared at him.
"What about you, Pine Tree? Who's your big crush, huh!?" A strangely defensive look passed over Dipper, and he sighed.
"A crazy lumber-jill who lives with her three brothers and her dad, out in the woods, off the grid, and is about three years older than me."
Mac's anger faded, and he smiled. "It's more normal than MY crush, Dip." Dipper chuckled, scratching the back of his head.
"Yeah, I guess it is." Ben slammed his hands on the table, his face turned bright red, a determined look stood out on his face.
"I've got both of you beat." He screwed his eyes shut, taking in a deep breath. "My crush is the most beautiful,
smart, snarky, and amazing girl I've known." He sat down in his seat, folding his arms with a cocky grin. "And she's MY cousin."

Dipper and Mac sat in silence, mouths open wide. "Woah, that is WAY weirder than yours, Mac." Dipper said,
feeling a bit uncomfortable. Ben folded his arms, frowning slightly. "She's been dating a bad boy though,
I'm tempted to actually horn in on her if he keeps it up..." Jack stood from his spot, walking away with his hands in his pockets.
"Darby, come on!" Ben shouted, his face turning back to normal. "You can't keep the Bots a secret." Dipper did a double take, from Jack to Ben,
eyes wide. "You guys knew each other before?" Ben nodded. "My Grandpa actually works with ALIENS, and so does Jack."

Dipper's eyes couldn't go much wider, but his grin almost split his face. "Really, Jack!? Can I meet them?!" Jack sighed,
his hands clenching into fists. "Fine, wanna know my love life, really?" He flipped his chair around, leaning forwards against the back.
"I've got all of you losers beat, because I have fallen in love with an 1000 year old woman,
who also happens to be a shape shifting ninja robot fighting a secret war on American soil." He sighed, a smile coming to his face.
"She's so beautiful, and I get to ride her all the time." The three boys were silent, bright red faces all around.
Jack's face went red and he glared at the rest of them. "She's a shape shifting robot, she's my motorcycle! Shit, you guys!"
He got to his feet, shouldering his backpack. "Look, she'll be here in a bit, so I'd appreciate it if you didn't let anything slip, okay?" Ben grinned, raising
a hand in a scout salute. "I swear, scouts honor." In a moment, Dipper replicated the motion he had shared with Wendy so long ago.
He smiled at the Raven haired teen, then glanced at Mac. "What? They'll just assume I met another Imaginary friend, so it's not like it'll matter."
Mac stated defensively, folding his arms. Suddenly, his phone buzzed. Mac's eyes widened as he fumbled with it, a blush on his face.
"Oh, hey Frankie!" He got to his feet, and he and Jack made their way towards the Shack's exit. Dipper hopped off his chair,
dusting himself off and glancing at Ben. "You going to see them off?" Ben shrugged, folding his arms and placing them on the table.

"Grandpa Max is still downstairs with your Grunkle Stanford, Gwen will probably be back in a bit."
The front door to the Mystery Shack flew open, and a blur of multi-color cotton rushed inside.
"Dip-Dip! You'll never guess who I ran into." Dipper smirked, an eyebrow raised. "The Ghost of Teenage Elvis Presley?"
The blur resolved into the form of Dipper's sister; Mable, who made an exaggerated grossed-out face.
"Ugh, no! I ran into another red head! Wendy must have family in town!" A knock on the door, and Mable rushed to open it. "YESSSSS!?"
A loud gasp, and a young woman with bright red hair was dragged back into the dining room. "SHE CAME HERE! See, Dipper!?"
Dipper's eyes widened, his eyes going to Ben who avoided the teen girl's gaze. "Hey, Doofus." The redhead said with a grin.
Ben sighed, a small blush tinting his face. "Hey, Dweeb." The girl, who Dipper recognized as Gwen, sat across from her cousin.
"Grandpa and Stanford still aren't done yet, huh?" Ben leaned back in his chair with a snort. "Those two nerds have been going at it since lunch."
As Ben and Gwen talked back and forth, Mable got a strange look in her eyes. Dipper recognized said look,
and promptly pulled her into the living room.

"What? Why can't I tell her?" Dipper pinched the bridge of his nose. "They're family, Mable. Cousins.
That's not exactly as taboo as it used to be, but we should let the two of them work it out."
Dipper shoved his hands in his pockets, turning towards the dining room. "If she really feels anything for him, she'll tell him. Or he'll tell her first." Dipper glanced at Mable, who seemed quite shocked. "Bro-Bro, when did you get all mature again?" Dipper chuckled,
pulling his phone from his pocket and glancing at his texts to Wendy. "I dunno, Sis. I dunno."