The third season of DC’S “Stargirl” premieres on Wednesday, August 31 at 8 p.m. ET. Joel McHale has been upped to a series regular this season. He plays Sylvester Pemberton/the original Starman.

Here’s what’s happening in the world of television for Monday, June 15. All times are Eastern. Stargirl (DC Universe, 9:00 a.m.): Last week, we saw Stargirl team up with “Wildcat.” This week, as ...