He'll always be her baby.

Mariah Carey shared a belated photos glimpse at her Halloween celebrations in an Instagram carousel post Nov. 8 which included a rare photo of her 13-year-old son Moroccan Cannon.

The "We Belong Together" singer was all smiles posing alongside her son in the adorable snap of their joint Alvin and the Chipmunks costume. Mariah—who shares Moroccan and his twin sister Monroe with ex Nick Cannon—dressed in a red hoodie as Alvin, while her son, in blue, was Simon. They both wore furry ears on their heads.

In another photo, Mariah beams as she holds Moroccan's hand and poses alongside another loved one who rounded out their trio costume as Theodore, dressed in green. The group all have lanyards around their necks from Universal's haunted R.I.P. Hollywood Horror Nights Hollywood Tours.

Of course, the iconic singing chipmunk wasn’t her only costume. Elsewhere in her slideshow post, Mariah rocked a plunging black glittery jumpsuit and cat ears as she posed alongside a ghost.

"Happy halloween!!" she captioned the post. "7 days later and during its time.. Heh serrryyy…"

The 55-year-old's caption referred to her annual Nov. 1 declaration that "it's time" to start celebrating the holiday season.

The Queen of Christmas recently opened up about her special relationship with her twins, saying that she didn't "even know how it's possible" that they're already teenagers.

"I love them so much,” Mariah exclusively told E! News in August. “They're really good kids. You know what I mean? I don’t think that they're bad or evil in any way like I was. They're really good kids and they're very smart and they're funny—and, you know, I'm the mommy.”

The Grammy winner went on to question what her kids really think about her as a parent.

"Am I mean? No. Am I lenient? Probably," Mariah said. "Because I don't want to be that person that's like the bleak one in the crowd and they don't want to be around me or something."

That being said, there's no question that Roc and Roe, as she affectionately calls them, support their superstar mother.

“They did want to come see the show the other night,” she said of her Vegas residency at Park MGM. “But, you know, I didn't know if they really wanted to come or if it was somebody else saying it. You never know!”

Mariah's twins will have plenty more opportunities to see their mom perform this holiday season, too, as she just kicked off her 21-date holiday tour earlier this week.

Keep reading for secrets about Mariah's signature Christmas hit, "All I Want for Christmas Is You."

Mariah Carey's 1994 album Merry Christmas is mostly covers—"Silent Night," "Joy to the World," etc.—but consequentially included three original tracks: "All I Want for Christmas Is You," "Miss You Most (At Christmas Time)" and "Jesus Born on This Day."

And while we may take that first one for granted now, Carey's cowriter on those three songs, Walter Afanasieff, pointed out that it takes big boughs of holly to take a stab at making new Christmas music. 

"Going into an original Christmas song, you've got to be really smart to know all the landmines that you're going to be stepping on," he explained in a 2014 interview with the American Society of Composers, Authors and Publishers. "If a smart writer writes a song and just boldly goes into the stereotype of jingle and mistle and frosty and Rudolph and Santa...Ugh, it just becomes a mess."

Carey's "genius," he added, was that she came up with an up-tempo "positive love song" that could be dedicated to anybody. 

And the third time was the charm, because "All I Want for Christmas Is You" was the last of the new tracks they wrote for the album, which they started working on in 1993.

Explaining their writing process, Afanasieff—who collaborated with Mimi on her first six studio albums—said that he would start playing. Then, "she starts developing a melody and melodic path," he told ASCAP. "We play a little musical ping-pong back and forth."

When Carey would sing something that took the music in a different direction, he'd follow, and "we just go back and forth," he continued. "Musically it was that big deal effort on 'All I Want for Christmas Is You.' It's a very simple arrangement."

In fact, he added, "At the time I thought it was overly simple and I didn't really like it."

Aside from Carey's pitch-perfect lyrics, "I tried to make it a little more unique, putting in some special chords that you really don’t hear a lot of, which made it unique and special," Afanasieff told Billboard in 2014. "I think that's one of the components that made it unique year after year. That part of it took maybe an hour, and then I went home."

First you hear the tinkle of the xylophone, then Carey comes in with her slow burn, after which the drums and piano get going and it's off to winter wonderland with sleigh bells jingling. So the recording studio must have been rockin' when the band laid down the track in the summer of 1994, right?

"That entire song is just me at the computer," Afanasieff told ASCAP, "and the only other thing real on there is the vocals."

When her album came out, Carey, the self-proclaimed "hugest Christmas fanatic there is," said she wasn't trying to compete with the Yuletide hitmakers of the past.

"I look at it as more of me giving my little contribution to the world of Christmas songs," she told CBS News in 1994, "and hopefully my fans will enjoy them and it will be something for me to sing during the holidays."

Carey has her own recollection of how "All I Want for Christmas Is You" came to be, and it generally doesn't involve another person being in the room.

"I just sat down, decorated a little tree and put on It's a Wonderful Life and tried to get into that mood," she told Cosmopolitan in 2019. "Then I sat in this small room with a keyboard and started doing little melodies and stuff." 

In the Amazon Music documentary Mariah Carey Is Christmas: The Story of "All I Want for Christmas Is You that same year," she did recall taking the track to "Walter A." to co-produce.

Addressing the legend that it only took 15 minutes to come together, Carey said on Nightline in 2023 that writing the song was a "pretty fast" process. "I was working on it by myself," she added. "So I was, you know, [humming the opening bar], writing on this little Casio keyboard."

While Afanasieff has enjoyed the rewards that have come with being officially credited as the song's cowriter and producer—"I own 50 percent of the song," he told Variety in 2019—he does sometimes feel like the queen of Christmas left him a lump of coal.

"She's the one that made the song a hit and she’s awesome," he said. "But she definitely does not share credit where credit is due."

Despite its surge in ubiquity years beforehand, "All I Want for Christmas Is You" didn't reach No. 1 on the Billboard Hot 100 singles chart until 2019.

But, it has reached the mountaintop every year since.

"I can't sit there and go, This has to happen," Carey told the Los Angeles Times ahead of the Nov. 6 launch of her annual (since 2014, minus 2020) Christmas tour. But, she added, "It's happened so many times that I’m thrilled. And should it happen again, I would be even more thrilled."

We'll see what 2024 holds, but Carey has at the very least gotten used to breaking her own records on Christmas Eve.

"All I Want for Christmas Is You" first claimed the record for most Dec. 24 Spotify streams in 2017, with 10.8 million plays, then surpassed the total in 2018 with 10.82 million and topped itself again in 2019 with more than 12 million.

On Dec. 24, 2022, it bested Adele's "Go Easy on Me" for most streams on any day, with 21,273,357.

And, a year later, "All I Want for Christmas Is You" set the new record for most streams in a day with more than 23.7 million, as well as became the most streamed Christmas song ever with upward of 1.5 billion plays.

You are forgiven if on first viewing you thought that the song the wildly talented object of Thomas Brodie-Sangster's affection sings toward the end of 2002's Love Actually was an original tune written for the movie.

Because what Olivia Olson's performance of "All I Want for Christmas Is You" basically changed history. Or altered fate, whichever, as countless moviegoers were compelled to track down the original.

"That's another phenomenon we should pay attention to," Afanasieff told Billboard in 2014. "Mariah Carey very, very rarely allows someone to record any of her songs in any film or television or any other medium."

And while she turned down countless requests for others to record her signature Christmas song over the years, she made an exception for Love Actually.

"I think she just had a particular fondness for the movie," Afanasieff recalled. "She liked the script and she liked the actors.  I'm sure she thought, 'It's a young girl, it’s the right time.'"

The "All I Want for Christmas Is You" universe includes a children's book and a 2017 animated film of the same name. According to ABC News, Carey's earnings from the song have been put at $72 million as of December 2023.

Before Carey's tune registered, it had been a minute since a Christmas song was also a massive hit.

If you count Wham!'s mournful "Last Christmas" as a holiday staple, we're talking 1984. If you prefer more pep in your reindeer's step, Jose Feliciano first wished us "Feliz Navidad" in 1970.

John Lennon and Yoko Ono made their cultural mark with 1971's "Happy Xmas (The War Is Over)," but that wasn't a huge hit in the U.S. at first. And it's more melancholy than merry, Carey herself calling it "pretty sad."

Really not since Brenda Lee's 1958 banger "Rockin' Around the Christmas Tree" (written by Johnny Marks) had there been such an upbeat addition to the canon that also sold millions of records. And suffice it to say, the Carey magic has not been replicated yet.

Comparing their song to "a cosmic occurrence that happens once every 5 billion years," Atanasieff told Billboard that "thousands of original Christmas songs have been written in the last 20 years...But for whatever reason 'All I Want For Christmas Is You' just became that song."

And, he added, it "was the last major song to enter that Christmas canon, and then the door slammed shut. It just closed."

As to why she thought the song had endured for three decades, "I think it's because I really, truly love the holidays," Carey told Nightline in 2023. "It's not fake."