With so many Canadian imports arriving on American network television, I’ve devised a simple test to determine whether a show hails from north of the border. Do the characters look more like real people than supermodels? If so, look for the “Made in Canada” tag. Is the comedy writing a little less gag-driven than Hollywood fare? It just might be written by Canadians.

Having recently failed miserably with the two stupid, soul-crushing, fake-documentary shows “High Society” and “Fly Girls,” the CW offers “18 to Life” (8 p.m., CW), a genial romantic comedy produced in Montreal and now in its second season on Canadian television.

With a plot at least as old as “The Mothers-in-Law,” a late-1960s sitcom recently released on DVD, “18” concerns two young-looking 18-year-old next-door neighbors who decide, rather impulsively, to get married before they even enter college.

Stacey Farber (“Degrassi”) stars as Jessie. She’s pretty in a rather human way, but she would never make a casting call for “Gossip Girl.” Her TV beau, Tom (Michael Seater), has a face for comedy.

The first half-hour offers a lead-up to their big day and not-so-big wedding night and often sparkles with dialogue and attitudes that should delight fans of “The Gilmore Girls.” The second episode (8:30 p.m.) saddles both the characters and the audience with the consequences of their life-altering deed and is not half as amusing.

But as summer-replacement series go, “18” offers an oasis of intelligence and occasional wit in a desert of reality television, cooking competitions and repeats. Savor “18 to Life” while you can. Like summer itself, it won’t be around forever.

• Doing “American Pickers” one better, “Scrappers” (9 p.m. and 9:30 p.m., Spike) mines for comedy in a Brooklyn, N.Y., scrapyard, filled with metallic refuse, tough guys and outsized personalities.

Tonight’s other highlights

• A dozen acts perform on “America’s Got Talent” (8 p.m., NBC).

• Amateurs hope to shine on “MasterChef” (8 p.m., Fox).

• An NBA star takes on fellow athletes at their own games on a new season of “Shaq vs” (8 p.m., ABC).

• “Shark Bite Beach” (8 p.m., Discovery) recalls bloody incidents in California and Mexico.

• “Warehouse 13” (8 p.m., Syfy) begins a crossover episode that continues with “Eureka” on Friday night.

• Alicia takes on a health care provider on “The Good Wife” (9 p.m., CBS).

• Tommy tries to help Colleen on “Rescue Me” (9 p.m., FX).

• The “Rachel Zoe Project” (9 p.m., Bravo) enters its third season of fashion management.