Two Democratic presidential hopefuls met earlier than expected this week, after a coincidence in travel schedules left them sitting near each other on a plane.
"Very funny, @united," Buttigieg tweeted.
Klobuchar responded, also on Twitter.
"And the debate begins… Good sitting by you @PeteButtigieg," she said.
The third Democratic debate, hosted by ABC News, will be at the historically black Texas Southern University on Thursday night.
This will be the first time the 10 highest-polling Democratic presidential candidates share the same debate stage.
The debate is scheduled from 8 p.m. to 11 p.m. EDT and can be seen on Univision, ABC, ABC News Live and locally on KTRK-TV.