SEASON PREMIERE: This improv comedy series began in a previous century, premiering on ABC in 1999. Since then, it’s resurfaced, after brief breathers, on what was then ABC Family, and, since 2013, on its current network, CW. The show’s first host was Drew Carey, who was succeeded, years ago, by Aisha Tyler, who continues to preside over the action and antics tonight, as Whose Line begins season 13 tonight. Familiar and very funny collaborators, making it up as they go along, include Ryan Stiles, Wayne Brady and Colin Mochrie.