The R-rated movie casts Jason Sudeikis as David, a low-level marijuana dealer, and Aniston as a stripper named Rose, who team up to smuggle drugs out of Mexico into the United States for a huge payday.
David also enlists the help of Casey and Kenny, two lonely, neglected teens -- played by Roberts and Poulter -- to help create the illusion of a wholesome family traveling on a vacation in a recreational vehicle.
During one scene, Rose and Casey try to teach Kenny how to properly kiss a girl because he is inexperienced and has a crush on the daughter of another family traveling by RV.
Of course, Melissa, the true object of his affection -- played by Molly Quinn -- walks in on the tutorial and is horrified because she thinks Kenny is kissing his mother and sister.
"It was kind of a bizarre scene. We kind of just laughed our way through it. It was a very awkward day for all involved," Poulter, 20, told reporters in New York recently. "It felt like lots of takes. Obviously, it's like, 'Boo hoo, tiny violin.' Because it was the greatest experience of that young boy's life, which he will remember forever. So, whatever Kenny went through, he got to do that. So, he came out on top, I think."
In another memorable movie moment, Poulter's character lands in the hospital after he is bitten by a tarantula that crawls up his pant leg.
"Kenny goes through it. High and lows, peaks and troughs," he noted. "The spider scene was interesting because we were literally by the side of the road with my pants around my ankles. We caused zero traffic, which was great. Lucky. But that was pretty embarrassing. Quite chilly, too. There was a good breeze going."
Co-starring Ed Helms, Nick Offerman and Kathryn Hahn, "We're the Millers" is in theaters now.