Required Custom Nodes:

ComfyUI-MediaMixer: Adds the two nodes needed for merging videos and selecting the final frame of a video.

ComfyUI-VideoHelperSuite: Load and save videos.

ComfyUI wrapper nodes for Pyramid-Flow: Best current Image2Video, although this method will will work as better models get image2video capabilities.
Download models from:

https://huggingface.co/Kijai/pyramid-flow-comfy/tree/main

Install to ComfyUI/models/diffusion_models and ComfyUI/models/vae

How to use:

Select a video file and enter a prompt for pyramid-flow, the last frame the the video you input will be used as the first frame for the new video generated. The input video is then merged with the output video to be saved.

There will likely be a noticeable change in motion in the video.

The first half of the video was a Mochi render.
If you would like to try this workflow with the same video I used you can use the YouTube Video Downloader node included in ComfyUI-MediaMixer to download this video.