The horizonal cast list has some issues worth mentioning:

1. Captions are very small and often abbreviated, requiring mouseover;
2. Emphasis on pictures makes it look nice, but trying to find someone by name or character name can take more time than necessary if the cast is extensive;
3. Horizontal scrolling on mobile can be problematic (more often than not the touch sensor registers the slight vertical move of a finger and starts vertical scroll instead of horizontal), and even on desktop clicking and dragging the scrollbar is clunky compared to using the scroll wheel.

I'd much prefer it to be replaced with vertical list, perhaps double (or even triple column on desktop if it is possible to fit the names beside the picture using normal-sized font without abbreviating), and single column on mobile. Adding the right arrow icon to the Actors header, leading to full list on a new view could be a satisfying solution as well. The list on separate view could be sortable by actor name and character name.

By the way, that little right arrow (the class="trakt-icon-circle-right" element) could be a bit bigger and easier to touch on mobile.