How to make a video
There have been a number of extensions for it since the early days of sd (and even just manually cutting frames and using inpaint / i2i, possibly with controlnet to extract specific details like depth or pose, combined with external tools like ebsynth). Oddly, no real native support was added to webui, so they're all very much lacking in standards of quality.
The most popular one currently (for 1.5) seems to be animatediff. Guide here (picked pseudorandomly): https://civitai.com/articles/2379/guide-comfyui-animatediff-guideworkflows-including-prompt-scheduling-an-inner-reflections-guide
Bear in mind it's still plenty of effort & computation for mostly mediocre results, but if you have those to spare it's a neat trick. Or just wait a few years.