Watch Blake Shelton Fail to Name One of Gwen Stefani's Biggest Hits

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Blake Shelton might want to brush up on his girlfriend Gwen Stefani's musical catalog.

Blake Shelton might want to brush up on his girlfriend Gwen Stefani's musical catalog.

The 41-year-old country star appeared on The Tonight Show Starring Jimmy Fallon on Monday, where he played the "Name That Song Challenge" with Fallon, in which The Roots play the instrumental version of a song that the two have to guess. But when The Roots played Stefani's massive 2005 hit, "Hollaback Girl," Shelton was at a loss.

After Fallon guessed the song before Shelton, the host couldn't contain his laughter.

"All I know is Blake is in a lot of trouble right now," he cracked as Shelton sat down on the floor. "You are in so much trouble, dude. I don't even know what to tell you."

"I came on this show to promote my album and I am losing everything!" Shelton quipped back. "Everything in my life!"

Shelton also appeared on the Today show on Tuesday, when he talked about his relationship with Stefani, particularly, with her three sons -- 11-year-old Kingston, 9-year-old Zuma and 4-year-old Apollo. 

"I never saw that coming, but it's so fun," he told Hoda Kotb and Kathie Lee Gifford of having children in his life. "At this point in my life, I kind of had put that, like -- 'Well, I guess that wasn't meant to be' -- and then all of a sudden it happens one way or another and it's like wow, I really missed out on a lot. So having them around is, I don't even know how to describe it, it's so much fun."

A source recently told ET that although Shelton and 48-year-old Stefani's relationship is stronger than ever, the two aren't making marriage a priority.

"There is no reason for them to rush into a marriage so they aren’t," the source said. "Both of them are happy and content with where their relationship is right now." 

"They are on cloud nine for each other," the source added. "They are perfect for each other. They know they have found their true soulmate."

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