Character swap AI: swap two people in one video
Character swap AI takes an existing video and replaces the people in it with someone from a photo, clothes included. The motion, the camera and the room stay the same.
You can do this in Motion Recast on UlazAI with Seedance 2 Mini or Seedance 2.5. A 10-second swap at 720p costs 125 credits on Mini and 760 on Seedance 2.5. You see the price before you generate.
One orange studio, 4.4 million views
On 20 September a 29-second clip went round X with four words under it: "sam killed it ngl". Two men perform in an orange studio with a microphone hanging between them. They look like Elon Musk and Sam Altman. They aren't: the performance belongs to someone else, and both faces were swapped in. When we checked on 23 September, the post had 4.4 million views and 17,400 likes.
Watch the original clip by @BasedDaedalus on X
Two days later Nate Herk posted the recipe to 600,000 viewers. His thread uses Higgsfield Genjutsu: upload the performance as a reference video, then upload one photo for each character. Mitte turned the same idea into a one-click app with two slots, "Left character" and "Right character", on top of the COLORS performance by Quavo and Takeoff.
Read Nate Herk's character swap thread on X
Every tool behind this trend runs on a video model that can edit an existing clip. We wanted to know what that costs per clip, and whether the cheap models can handle two people at once.
Can a cheap model swap two people at once?
We made an 8-second test clip of two men in dark suits in a hotel lobby, at 720p. Then we created two portraits that look nothing like them: a bearded man in a mustard sweater and a woman with a platinum bob, round glasses and a red bomber jacket. Every model got the same clip, the same two photos and the same instruction: keep the motion, camera and lobby; turn the left man into photo 1 and the right man into photo 2.
We ran it on 23 September through our video provider KIE. The prices below are what KIE actually deducted for that clip (200 KIE credits cost $1). They are not UlazAI prices.
| Model | Two-person swap, 8 s | Cost of this clip |
|---|---|---|
| Seedance 2 Mini | Both correct, gestures and lobby unchanged | $0.40 |
| Kling 3.0 Omni | Both correct | $0.80 |
| Wan 2.2 Animate Replace | Wrong: replaced the same man twice | $1.00 (two runs) |
| Seedance 2.5 | Not run on this clip | about $3.04 at list price |
Both Seedance models charge per second over the source clip plus the output. At 720p that is 5 KIE credits per second for Seedance 2 Mini and 38 for Seedance 2.5. For Mini, KIE deducted exactly that: 80 credits for 8 seconds in and 8 seconds out. The Seedance 2.5 figure is the same sum at its list price, because we did not run 2.5 on this clip.
We also ran a 5-second clip with one person, a woman in a grey hoodie walking towards the camera. Seedance 2 Mini, Kling 3.0 Omni and Wan 2.2 Animate all turned her into the bearded man, including his smile at the end. Seedance 2 and Seedance 2 Fast returned "Internal Error" on that clip and produced nothing, so we have no verdict on them.
Wan swaps one face perfectly and the second one not at all
With one person in the shot, Wan 2.2 Animate Replace kept the framing more exactly than the other two and cost $0.31 for 5 seconds. Its API takes one video and one photo, with no way to say which person should change. On the two-person clip the first run replaced the man on the left. The second run, fed the first result and the woman's photo, replaced that same left position again. The man on the right never changed. Wan also returns video without sound, so you have to put the original audio back yourself.
Is Seedance 2.5 worth six times the price for this?
For a meme-length swap of two people, we don't think so. Seedance 2 Mini got both identities right, kept the gestures and left the lobby alone, for about an eighth of the Seedance 2.5 list price on the same clip. On UlazAI a 10-second swap costs 125 credits on Mini against 760 on Seedance 2.5, which is why Motion Recast now offers both.
Our own test has a weak spot, though. It is one clip with a static camera, even light and two people standing still. Fast dance moves, hands crossing a face and profile shots are where cheaper models usually slip, and we have not tested any of those. We also never ran Seedance 2.5 on the two-person clip. Mini also stops at 15 seconds of source video. Longer clips still need Seedance 2.5.
Neither model produced the famous-face version
We also tried the viral format itself: a 12-second clip of two well-known politicians performing in an orange studio, to be swapped into our two fictional people. Seedance 2 Mini refused with "The request failed because the output video may contain sensitive information". Kling 3.0 Omni failed with a generic error. Neither run was charged.
That fits the rules on UlazAI as well: only swap in faces of people who have agreed to it, and don't make a video that pretends to be someone else. The demos on this page use AI-generated people only.
Swapping two people in Motion Recast, step by step
- Trim your clip to 15 seconds or less, and start it on a frame where both faces are clearly visible.
- Open Motion Recast and upload the clip.
- Upload the photo for the person on the left first, then the photo for the person on the right, both in the Character slot.
- Choose "Swap one element", set the target to Character and describe the mapping in the short description, for example: "left man becomes photo 1, right man becomes photo 2".
- Pick Seedance 2 Mini. The price for your clip appears before you generate: a 10-second swap costs 125 credits at 720p and 60 at 480p. The same clip on Seedance 2.5 costs 760 credits.
Our test went straight to the model with a longer instruction than the short description in step 4, and we have not yet run that short version through Motion Recast. This is the exact text we sent:
"Keep this video exactly as filmed: same motion, gestures, camera, lighting, lobby background and timing. Change only the two people: the man on the left becomes the man from reference image 1 (same face, hair and mustard sweater); the man on the right becomes the woman from reference image 2 (same face, blonde bob, glasses and red bomber jacket)."
A photo instead of a video? Then you need a still-image tool: AI face swap changes only the face, and AI head swap also takes the hair and head shape. A character swap in a video changes the whole person, clothes included, which is why the woman in our test arrived in her red jacket.
Other options on UlazAI: Kling 3.0 for text and image to video. Wan Animate 2 has been announced but can't be used yet.
Hands, spins and a moving camera come next
A clip where people stand and talk is the easy case. The real test for Seedance 2 Mini is a dance clip with hands in front of faces and a camera that follows the action. If Mini holds up there, Seedance 2.5 becomes a tool for long clips only. If it doesn't, the extra cost buys something you can see.
Sources: @BasedDaedalus on X · Nate Herk's thread · Mitte Hotel Lobby Character Swap · KIE Seedance 2.5 pricing · KIE Seedance 2 Mini pricing · KIE Wan 2.2 Animate pricing · KIE Kling 3.0 Omni transformation