Google has removed audio about the movie Beauty and the Beast which played out unprompted on Google Home.
"By the way, Disney's live action Beauty and the Beast opens today," the smart speaker said after listing the time, weather and travel update.
In a video posted on Twitter, it then talked about the plot and suggested asking it about main character Belle for "more movie fun".
Google denied that the material on Home was an advertisement.
It appeared as part of a "My Day" feature where the digital assistant provides an update which can include calendar events and news bulletins.
"This wasn't intended to be an ad," said a spokeswoman.
"What's circulating online was a part of our My Day feature, where after providing helpful information about your day, we sometimes call out timely content.
"We're continuing to experiment with new ways to surface unique content for users and we could have done better in this case."
The device is not yet available outside the US.
The tech giant has experimented before with including what it calls "seasonal timely content" on the Google Home device without it being requested.
Previous material on the themes of Black History Month and the Oscars has also run.
The rise of digital assistants presents a "tricky conundrum" for advertising sales, said analyst Ben Wood from CCS Insight.
"Unlike adverts inserted on a screen which can be glossed over, anything presented in an audio format risks being incredibly intrusive," he said.
"The most likely outcome will be that there would be ad-funded voice assistants where the user gets a discounted device in return for accepting adverts."
He added that Google faces a different challenge to Amazon, which markets rival home assistant the Amazon Echo.
"Google's primary business model is predicated on advertising," he said.
"Whereas for Amazon its about transactional revenue where a voice assistant like Echo can help drive sales."