Melissa Benoist and Grant Gustin 'Glee' Runion in New ‘Supergirl/Flash’ Crossover >>

Tonight, 'Glee' fans are in for a special treat. Marley Rose actress Melissa Benoist and Sebastian Smythe actor Grant Gustin are coming together into tonight’s all new 'Supergirl/Flash' crossover special, “The World’s Finest.”