Mandy Moore freaked out by robot babies on This Is Us set

Mandy Moore finds it awkward whenever she has to work with a robot baby on the set of This Is Us.

The actress stars as Rebecca Pearson in the hit NBC show, which follows the lives and connections of several siblings who all share the same birthday.

This Is Us episodes weave through stories of the past and present using flashbacks, which means Mandy often has to act with babies, and the occasional robotic version when real newborns aren't available.

"There's a new rule with Homeland Security that anybody who works has to have a photo ID," she shared during an appearance on The Tonight Show Starring Jimmy Fallon on Tuesday night (10Oct17). "So what mom is going to schlep her child, her newborn, to the DMV (Department of Vehicles), to get an ID. So, often times when we're shooting with small babies they're either baby dolls or they have this one robotic baby. It's weird guys."

Mandy added that she really has to try her best to focus when working with robotic dolls as they make odd noises and movements.

"We were just shooting an episode where I have two very emotional scenes where I'm talking to the newborn in the hospital and I go to put my hand on the robotic baby and it's like vibrating and making weird movements. And you are just like, 'Nope this is a real child,'" she laughed.

With This Is Us, Mandy is joined by an ensemble cast including; Milo Ventimiglia, Chrissy Metz, Justin Hartley and Susan Kelechi Watson. But the actress swears it is Sterling K. Brown, who portrays Randall Pearson, who is the most professional during takes.

"I think Chrissy and I are the most emotional. But I think Sterling gets the award for best crier. I feel like he's literally at the point as an actor (where he asks the director), 'What eye do you want me to (cry from)? The dramatic single tear drop down my cheek?' He's that good."