Describe the students' full names and GPAs under the supervision of the most popular professor.
student's full names = f_name, l_name; most popular refers to MAX(popularity);
SELECT T3.f_name, T3.l_name, T3.gpa FROM prof AS T1 INNER JOIN RA AS T2 ON T1.prof_id = T2.prof_id INNER JOIN student AS T3 ON T2.student_id = T3.student_id ORDER BY T1.popularity DESC LIMIT 1