The iHeartRadio Music Festival, The Castle Premiere and More on TV Tonight

Concerts, reunion shows, and the return of some of the best primetime dramas—we'd say that's not too shabby for a Monday. Here's what to watch and why:

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The iHeartRadio Music Festival. 8pm on The CW. The concert that happened two weeks ago in Las Vegas gets a two-night TV special. Part 1 includes performances from Taylor Swift, Ariana Grande, Usher and more.

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Mom. 8:30pm on CBS. Allison Janney won the Emmy for this show, which premieres tonight with season 2. Christy will be doing some gambling, which we guess is better than Christy doing drugs or sleeping with bad guys, right?

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Are You The One? 10pm on MTV. This special is a combo of a reunion show of the season 1 cast and baby shower for the show's biggest success story, Amber and Ethan, who are expecting their first child in December.

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Castle. 10pm on ABC. Beckett learns more about Castle's car crash and is close to finding him in the season 7 premiere.

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The Hispanic Heritage Awards. 10pm on PBS. The annual ceremony, held in DC, honors Hispanic stars who've made a difference. This year's honoree is Zoe Saldana!

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What will you be watching tonight? Tweet us @OKMagazine.