It is no secret that one of the reasons why Outlander is such a hit to fans is the undeniable chemistry between the lead stars Sam Heughan and Caitriona Balfe. However, after working closely together for years, there are still things that Balfe did not fully accept on her on-screen husband. 

Balfe and Heughan have been playing Claire and Jaime, respectively, for the past five seasons of the Starz series. The Irish actress admitted that she and Sam have a great working relationship and they rarely argue on set. However, there is one habit that irks her about the Bloodshot actor. 

Balfe jokingly said she always has an issue about Heughan's timekeeping. She said it can sometimes annoy her especially if she was often left standing while waiting for Sam. 

But then Balfe confessed she may probably annoy the Scottish actor too. The Ford v Ferrari actress hilariously said she bossed Heughan around so he could get mad at her. 

Balfe added that the secret of their great relationship on set was their agreement when they started the series that they should have each other's back. They support each other as a team and that for them creates a relaxed working environment. 

Caitriona Balfe and Sam Heughan clearly have fun filming the fan-favorite TV series. Their chemistry was evident both on and off the screen. This was also what showrunner Ronald D. Moore saw in them during their screen test together. 

Moore previously opened up about how they cast the two as the on-screen husband and wife in the TV adaptation of Diana Gabaldon's novels. In the Outlander Season 3 Collector's Edition Blu-ray, the series shared a sneak peek of Balfe and Heughan screen test. 

Apparently, Heughan has been cast first. Moore said it was the final test before they decide if they will give the role of Claire to Balfe. The Outlander boss admitted that they already have the feeling that Balfe can do it but they do the screen test anyway. Sam and Caitriona have to do the screen test together to see if they could show the right emotional connection between the two characters. 

The EP said after the two did the scene together, they kept the camera rolling to see how the two actors interact in a more relaxing environment. Moore said what they saw was a "genuine affection" and good humor between the two. The on-camera chemistry of Sam and Caitriona is on point, and so is their off-camera interaction.