Although every cactus I grow is the same, they are, of course, all different. It's the unusual that I particularly find interesting. Here is a page devoted to some of the unique characteristics and my names for them:

The Hoverfly that visits the flowers: there are very few bees and as far as I can remember, never any wasps, that are interested in visiting the flower of the cactus when it blooms. However, almost every flowering is accompanied by a visit from a hoverfly or two. Here's one:

Hover Fly
Scorched hole

The result is that a new baby grows over the hole hence the name of "Crowning". Here's an example:

Turning Orange:  I think that this is another response, like the above, to being scorched with concentrated sunlight. The flesh turns orange at first, later it goes brown and it then hardens and becomes wooden. Here's an example:

Turning Orange

Other phenomenon will be explored further soon, these will include: The Leaf-Cutting Bee Visits & Water-Towering