EXCLUSIVE:  Judd Apatow has brought a murderer’s row of comedians around Glen Powell for his new Universal Pictures comedy,  The Comeback King . The call sheet includes Leanne Morgan ( Leanne ), Kumail Nanjiani and Atsuko Okatsuka — who recently released the lauded Hulu specials  Night Thoughts  and  Father — Vanessa Bayer ( I Love That for You ), Tig Notaro ( The Morning Show ), Chris Fleming ( Chris Fleming: Live at the Palace ), Mike Birbiglia ( Don’t Think Twice ), and Nashville personality Big Fella ( The Runarounds ). Character details are under wraps, and we still know little about the plot of the film, other than it revolving around a country western star in free fall, played by Powell, who wrote the script with Apatow. Other previously announced cast members include Cristin Milioti, Madelyn Cline, Stavros Halkias and Li Jin Hao.…