Given the popularity of the function on TikTok, it'll come as no surprise to see that Instagram is working to add a remix option into its Reels clone, which it's now being tested with some users in the app.

As you can see in this example, posted by user @riodevale on Twitter (and shared by Matt Navarra), the new 'Remix this Reel' option is now appearing for some users in their Reels options menu. Once selected, users can then create a reaction clip, with the original and your new video playing side-by-side.
As noted, remixes - known as 'Duets' - have been a key engagement tool on TikTok, giving users the capacity to respond to trends, and engage in viral memes.
That's helped to make Reels a more interactive, inclusive tool, while also sparking the creativity of users without them having to come up with their own, original content.
Instagram's actually been working on its remix option since Reels was first released.
Last October, app researcher Alessandro Paluzzi found the first mention of 'Remix' in the Reels code, with a feature that would allow users to choose whether their Reels would be available for remixing or not. Since then, Paluzzi has found several more elements in testing, including this introductory screen for the option.

Some users reported seeing the option in live testing back in December, but now, it seems that more people are getting access to the new Remix option in their Reels tools in the app.
It's not at full roll-out stage as yet, but you may have the option in your version of IG.
Interestingly, this week, we also reported that Snapchat is working on a similar option for Snaps. YouTube's also developing remixing tools for its TikTok clone, 'Shorts', which it released, in beta mode, to some US users just last week.
As noted, it's a simple, engaging way to spark user creativity, which reduces the onus of originality, but can also guide users into creating their own trends by engaging with popular remixes.
As such, much like TikTok in general, it makes sense to see other platforms trying to replicate the tool - and it looks like we're going to see a lot more remixes moving forward.