Shoot yourself in front of a green screen and chroma key everything except you. Place that video on the track above the video you want to replace.

Thanks. What about the background of the star. They are standing side by side

It possibly could be done if the original shot is perfectly steady and without any movement behind the person to be replaced. For a bit of a lark some years ago in a project, I replaced a politician addressing the UN General Assembly with myself looking like I was doing the same. I took still images of the UN podium (in front of the UN's green marble wall) and, using Corel PaintShop Pro, I used its clone tool to replace the outer areas of the 'real' speaker with more of the green marble background - then chroma-keyed my green-screened video over the PaintShop Pro'd image. It worked quite well but I had to do some other trickery to include the lectern, reading light and microphones.

Getting back to your project ... if the camera is static and there is no movement behind the person to be replaced, you could take a screenshot of the image and use a photo editor to clone the background over as much of the person as needed so that when you put your chroma-keyed video over the still image, your video covers all of the replaced person throughout the shot.

In Vegas Pro, split screen the original video with the still image and then place your chroma-keyed video (of you) over the still image. In addition to the static camera and no bg movement issues, another consideration is that the two original people need to be separated so as to enable a clean split screen.

It may be necessary to add a film grain FX over the still image to help it match the grain look of the original video.

I hope this helps.

@perrywynkles Also see if you have Color Corrector (Secondary) FX in vp15... it can do everything ChromaKey does with added limits based on saturation and brightness. Can make a blue screen work even behind a subject with blue eyes wearing blue clothes. Also, for optimal operation of both of these FX, set project resolution and preview to Best.

@perrywynkles Also see if you have Color Corrector (Secondary) FX in vp15... it can do everything ChromaKey does with added limits based on saturation and brightness. Can make a blue screen work even behind a subject with blue eyes wearing blue clothes. Also, for optimal operation of both of these FX, set project resolution and preview to Best.

"Also see if you have Color Corrector (Secondary) FX in vp15"

Yes I have thank you