While watching the videos, I created my own caricatures based on the original pictures. I still need to exaggerate features more and my images are not as cartoony as I would like. However, I am quite happy to see that my pictures do seem (at least to me) to resemble the celebrities they are supposed to represent.
I haven't added colour as I am focussing at the moment mostly on straight pencil illustration. Here are the first three images: