Last night, they both appeared on the finale of The Voice, so they were bound to run into each other.
And it looks like they're both taking each other's comments pretty well, as they made a hilarious video that Katy posted online.
"You're following me," Katy says to Niall, in the video captioned "@niallhoran stage 5 clinger."
"I'm everywhere," he responds, looking confused and scared... in a funny way... before he runs off. K then.
Can this #Kiall thing end now? Please?