The actor remembered his time working with the pop star on the 20th anniversary of their film, 'Crossroads.'
"I remember her being so down-to-earth, like disarmingly down-to-earth," he told ET's Cassie DiLaura at a press event for his upcoming film, Barbarian.
Long and Spears both appeared in the 2002 feature Crossroads, which told the story of three teenage girls -- Lucy, Kit and Mimi -- who embark on a cross-country road trip to Los Angeles. Spears appeared alongside Taryn Manning and Zoe Saldana as the three girls, and Long played an old friend with whom Spears' Lucy had a short fling.
"I remember being struck by how normal and easygoing she seemed for all the hoopla surrounding her," he continued, "and then a couple years later seeing what the paparazzi did to her, it was really sad that we live in that kind of culture that can do that to a human being. She was so nice to everyone."
Long's latest film, Barbarian, is the story of a young woman -- played by Georgina Campbell -- who discovers the rental home she booked is already occupied by a stranger (played by Long) and also potentially possessed by another mysterious being.
The film comes from the same production team as The Ring, IT, and The Grudge, and Long promises it will hold up against that hard-to-beat collection of scary movies.
"I think it'll be a worthy entry in that canon," he said.
Long's girlfriend, Kate Bosworth, also briefly appears in the film. "She had a fun cameo that she's so good in," Long said, adding that she has seen the film and "had said the best things about it."
Long’s co-star added her own excitement for the film's release. "It's definitely got those moments that are going to scare people and make them cling to their seat," Campbell said.
Barbarian hits theaters on Sept. 9.