"Dinosaurs in Love" may not be a typical bop, but you cannot deny a hit when you hear one.
Clocking in at a brief 60 seconds, the song has all the elements of a classic Mesozoic love tragedy: Dinosaurs fall in love, eat people, and have a party, then they get wiped out by a big bang without saying goodbye to each other.
Its devastating plot twist has also made a lot of people cry, judging by the response to Rosenthal's viral tweet of the song.
Rosenthal, a singer-songwriter, told BuzzFeed News that "Dinosaurs in Love" came together pretty organically.
He has a home recording studio, and he's written songs with both Fenn and his other daughter, a 6-year-old, he said.
This time, it was just Fenn around, and she wandered into his studio and asked to do a song.
"She's by the microphone, she's got the headphones on, she starts singing, and she does as much as she can," he said.
"And then eventually after she's done enough little bits of it, it kind of all fits together," Rosenthal added. "Sometimes we have little breaks. ... She gets bored, she wanders off, she comes back in."
Rosenthal gives her prompts while she's singing, one of which he included in the final cut. Then he puts the different parts together to make the song.
"In terms of her singing and her timing, nothing's altered, but it's done in a couple of sections," he said.
The subject matter surprised him a bit, because Fenn didn't seem especially interested in dinosaurs.
"I genuinely couldn't tell you why she wanted to do a song about dinosaurs," Rosenthal said. "She's got no particular affiliation with dinosaurs at all. They're not something she particularly cares about or not, this is just what was in her head at the time."
They've been to the Natural History Museum a few times, but he said it's hard to know to what extent she understands dinosaurs and how they went extinct.
"I was pleased because it was obviously fairly accurate," he added.
The video of Fenn's song has been viewed more than 600,000 times since her dad posted it online Tuesday — even the Spotify Twitter account asked for an official release date.
Rosenthal said the response on Twitter was unexpected, but he wasn't terribly surprised.
"I know what a nice song sounds like and I was like, That's a really nice song. And it's quite potent because you've got a little [almost] 4-year-old talking about things dying, and so many things are dying currently in the world," he said. "I think it's just kind of evocative of the moment."
Rosenthal said he wouldn't mind if Fenn followed in his footsteps to become a musician, but "she probably already achieved more than me in one day than I have in my whole career."
She remains oblivious about her newfound fame, however.
"She has absolutely no idea," Rosenthal said. "She literally did this song, we listened back to it five or six times, and then she's on with the rest of her life."
And that, folks, is a true icon.