Frankie Valli, Mariah Carey second-rate as 'American Idol' crowns season 12 champion

"American Idol" is going to crown its season 12 champion tonight -- but first we have to suffer through what's become in recent years a string of second-rate guest performers, matched up with the finalists.

The five guys who made the finals then return with a cheesy montage of Frankie Valli songs. Because, you know, in 2013 that's the sweet spot for guys in their 20s hoping to make it big in the music industry. 

Because if so, those grandkids would have no idea what made Valli great based on his performance tonight. They could only conclude their grandparents are tone deaf.

Back from commercial, and Mariah Carey is in the middle of a random performance of songs you remember her singing well in the past. In her mind, she's probably conducting a master class.

She's really embarrassed herself as a judge this season -- most of her comments have been unintelligible, she's loved everything and thus has been unable to help any of the contestants.

Probably the best part of her being on the show has been as a target for Nicki Minaj's zingers and eye-rolling.