The YouTube Kids app can sometimes feel like a shopping channel, with videos upon videos of kids unboxing toys. The clips star pitch-kids who have mastered the art of the sale.

These YouTube child stars are good at what they do, unpacking new toys and showing off all the parts and how to play with them. You'll find Play-Doh, Disney princesses, Legos and more on display in an almost fetishistic fashion. The kids are sometimes paid handsomely by brands, too, but the videos aren't labeled as marketing.

One of the top child YouTube stars, Evan of EvanTubeHD, is a cherubic tyke whose toy playing is almost hypnotic. He could be the best pitchman since the late Billy Mays, and Evan has 1.5 million YouTube subscribers.

He also is part of the reason that parent groups and anti-commercial organizations want regulators to come down on YouTube and its kids-focused app. Campaign for a Commercial-Free Childhood and the Center for Digital Democracy have met with the Federal Trade Commission to complain about YouTube Kids content.

They have issued two formal protests and want YouTube to change how it labels certain videos or stop showing ones that the groups consider to be advertising.

"It's unfair to children how they were mixing ads with content, sort of doing things that you can't really do on TV," said Aaron Mackey, a Georgetown Law professor who who works with parent groups on these topics.

There are animated shows featuring Barbie and the toy franchise's Dreamhouse product, and there are video clips that are basically McDonald's commercials. The groups also claim some of the content, which is accessible through the app, is too mature for kids.

The unboxing videos are a focal point of the protests. "Unboxing" has become a popular genre for adults, too—whenever a new Apple product is released, for instance.

"It's all very problematic—unboxing videos, in particular," Mackey said. "Children deceived into thinking this is content, a kid playing with a toy, when it's a kid selling them a toy."

Of course, many unboxing videos are not even created by brands themselves, and are simply user-generated content that happens to be quite popular. Also, videos posted by brands are often among the most viewed on the platform, and are not official advertisements.

The YouTube stars are bankable talent, and video producers like Maker Studios sign them to lucrative deals. Maker is owned by Disney, a big beneficiary of unboxing videos.

The parent groups would like better labeling of commercial videos on apps like YouTube Kids. Mackey said the rules they fought for on television advertising should have a counterpart in the digital space—like requiring shows to clearly state when they switch from regular programming to advertising.

Mackey said the groups have already met with regulators to discuss their concerns, and the FTC is looking into it.

The FTC complaint wasn't the only indication that some users were unhappy with the app, however. There are a number of reviews in Google's Play store, where the app can be downloaded, that show some users want more control over what videos are available to their children.

The first reviewer of the app had this to say, exemplary of a number of comments calling for more parental controls: "Better filtering options needed. I want to be able to reject specific videos or channels and have them never play again. "

The app has been downloaded millions of times, and does has more than four out of five stars on average.

"We work to make the videos in YouTube Kids as family-friendly as possible and take feedback very seriously. We appreciate people drawing problematic content to our attention, and make it possible for anyone to flag a video. Flagged videos are manually reviewed 24-7, and any videos that don't belong in the app are removed," Google said in a statement. "For parents who want a more restricted experience, we recommend that they turn off search."