There are a bunch of apps that do this, here is one of the popular ones https://remini.ai/.
For more DIY you could use a comfyui or automatic1111 google collab or if you wanna go cheaper use a service like vast.ai and then search on youtube “face swap comfyui” or “face swap automatic1111” for a bunch of tutorials
OP if you interested they started by parodying Seinfeld until the AI got a bit too … https://www.theguardian.com/us-news/2023/feb/06/nothing-forever-twitch-ban-seinfeld-parody-ai