"Why is it not just straight forward on this show?," the singer said.
With Halloween just around the corner, the daytime talk-show host kicked things off by asking the former One Direction member if he still hangs out with his old band mates. Horan happily started to discuss how Louis Tomlinson came to support him at one of his shows and Liam Payne and Harry Styles were meeting up with him in the next few weeks.
And then out of nowhere, a man dressed as Styles jumped out of the small table sitting in between the duo on stage.
After a loud scream followed by a long moment of silence with DeGeneres holding back her laughter, Horan said: "Cardiac arrest nearly happened there. Why is it not just straight forward on this show?"
In honor of Ellen's latest surprise, here are more of the talk-show host's top scares (so far):