Britney Spears has already earned rave reviews from her How I Met Your Mother castmates. Now the pop star is sharing the love.quote:"Working at How I Met Your Mother has been so terrific," Spears says. "Everyone, including the cast, the crew and the producers, has been wonderful and Abby is such a fun girl to play. I'm having a blast!"The singer, who arrived on set promptly at 7:30 a.m. Wednesday morning, is expected to continue shooting on Thursday afternoon following a visit with her sons. "The filming schedule was worked out so that she could still keep her visitation with her two boys," a source tells PEOPLE. "That was very important."Apart from her assistant, Brett, the singer was joined on set Wednesday by her father, Jamie, and mother, Lynne. "Her parents kept thanking everyone onset ... saying this is just what their daughter needed," the source says.Plus, Spears was quite prepared for her role. While castmember Josh Radnor joked that the singer "knew her lines better than I knew mine," a show source confirms that the singer was "very sweet and cute and she chewed gum obsessively on set."If all goes well, could this be a continuing role? Says the show source: "She had a lot of fun doing it and she even mentioned extending her character. Who knows? She got along really well with everyone."Spears' guest turn on How I Met Your Mother is scheduled to air March 24.