Kate Gosselin's son Collin unexpectedly appeared on the season finale of Kate Plus 8 this week, and viewers have been wondering why.

Collin, one of Gosselin's 12-year-old sextuplets, was enrolled in a live-in learning facility to address his previously-disclosed "special needs," a decision Gosselin had called "necessary" late last year.

Although Collin has been absent from the latest season of Kate Plus 8, he suddenly and surprisingly appeared on Tuesday's episode of Kate Plus 8. Collin participated in family game-night and conducted a joint interview with his two brothers Joel and Aaden.

"The reason he was on the show is that it was shot before he went away," an insider told People, "and sometimes footage airs out of order."

In November, Gosselin -- who also has 16-year-old twins Mady and Cara with her ex-husband Jon -- said she followed doctors' advice by sending Collin away from home for the help he needs.

"I don't know what the road ahead entails, but I'm very happy with the care that he's getting, and am still completely comforted by the fact that he is so clearly exactly where he needs to be," the 41-year-old reality TV star had said.

"It comforts me as a mother -- because when you, as a mom, can't give your kids what they need, it is a huge comfort to find people who can."

Gosselin initially opened up about her decision to enroll Collin in the program in August 2016, telling People that he was learning "the skills he needs to be the best him he can be."

"Collin has special needs. [There's] a fairly fluid diagnosis of what those needs are, but he needs to learn certain strategies to help him deal with things," Gosselin revealed at the time.

"This has been a struggle we've had for a very long time, and it's one I've dealt with on my own. I've felt very alone in this. By the same token, it's not something that has only impacted me or him -- our entire family has been impacted."

She added, "We miss him so much, so it's been hard because there is a huge hole in our family without him here. But it comforts us to know he's where he needs to be right now, and I can feel good about that."