Lori Loughlin's "actress side" came out during her first court appearance over her part in the college admissions cheating scandal, with US media outlets reporting on her bizarre behaviour.
The Full House star appeared cheery and looked "like she was at a red carpet" both inside and outside court, raising the eyebrows of onlookers.
Loughlin and her husband Mossimo Giannulli are accused of paying $US500,000 to get their daughters into the University of Southern California as members of the school's rowing team.
But neither YouTuber Olivia Jade or Isabella Rose were rowers, with the two girls posing for photos on rowing machines so their parents could allegedly create fake athletic profiles.
But Loughlin's alleged criminal behaviour didn't stop crowds from gathering outside a Boston court on Wednesday, with fans wearing Aunt Becky masks and yelling her name as she signed autographs on her way in.
Mackenzie Thomas shared a video to Instagram of Loughlin smiling as she asked the actress to pay for her college tuition.
The university student later told Vanity Fair she had been surprised by the star's behaviour.
"Honestly, Lori's demeanour was like she was at a red carpet. It was reminiscent of when a celebrity walks out of a hotel, and fans are waiting for them," Ms Thomas said.
"She had that type of smiley, like, 'OK, I'll pose for a picture, I'll sign autographs.' She just looked like she was having the time of her life."
Inside court, Loughlin's lighthearted demeanour continued, with the New York Post reporting she "turned on the star power".
The Full House star "flashed a 1000-watt smile as she approached the prosecution table and shook hands with each of the four feds handling her case," the publication claimed.
When asked by a Post reporter how she was going, Loughlin replied: "I'm great."
"How are you?" she added, patting the Post reporter on the arm.
After Loughlin's unexpected behaviour made headlines a source told E! News the actress had acted instinctively, not realising how it would look.
"She was obviously extremely nervous and the actress side of Lori came out. She doesn't know how else to be in public," the insider said.
The source added that Loughlin had never received negative attention before so was in "uncharted territory".
"Her natural reaction was to just smile and try to be lighthearted," they claimed.
"She's always been so well loved and charming, that's the part she knows how to play in public."
Loughlin's behaviour contrasted with Felicity Huffman, who appeared stony-faced and did not interact with the crowd as she made her way in.
The 56-year-old Desperate Housewives star is charged with paying $US15,000 to have her daughter's SAT answers corrected.