I know what you're talking about. I just don't know how to do it, because there's not a full tutorial on how to make videos like how they do. I don't know about KiddCab or Kasper Beats because I've never checked out their videos, but as far as mjNichols, SigmaBeats and some other YouTube producers I've come across. That effect is called "light leaks". I guess they find a video with that effect, and place it on the still image. I'm trying to figure it out like you though.