The .7z extension is a legitimate compression format. You will need a program like 7-Zip or WinRAR to open it.
Because this file name is often used as "clickbait" in edgy or fringe corners of the internet (like 4chan or Discord), archives with this name are frequently used to disguise malware, trojans, or "screamer" programs . Bart video.7z
If you downloaded this expecting a rare piece of television history, you will likely find a distorted fan edit at best, or a security risk at worst. If you haven't opened it yet, it is highly recommended to on the archive before extracting the contents. Bart video.7z