They use wit, sarcasm, and have impeccable comedic timing.
Most people know a "Duo", and make sure to invite them to all their parties, family gatherings, and social events.
"Uh, yeah. If we want to make a good impression, we'll need them to keep everyone going."
"I know someone you might click with!"
"You mean, like become a Duo?"
"We have to make sure to see The Duo this summer. Family gatherings are always so boring when they aren't around!"