I once saw an article posted by a Catholic page, about what a life-changer it can be to have a skull on your desk. After having written most of this post, I just now actually read it and would highly recommend it! https://aleteia.org/2017/09/12/memento-mori-how-a-skull-on-your-desk-will-change-your-life/
I can certainly see why this would be the case. A skull is a symbol of death—human death. Death can seem so far away from us, even when those close to us die; we might not think about how that will eventually be each and every one of us.
Does that make you think at all? About how you spend your time, perhaps?—what you do with it, how wisely you use it, what you put off or allow yourself to be held back from? It should. For one day, you will resemble that skull: one day, you will die. You will feel life slip from your grasp. What will you have done in the time leading up to that? How many regrets will you have? Will you be ready for what comes after it?
And not just you will one day die. One day, your loved ones will die (perhaps in your own lifetime), or perhaps grow distant; one day, every physical thing you possess will be lost to you—your physical abilities, your possessions, perhaps even your mental faculties.*
What does this mean? That we should cling to all these things with desperation? Not at all. It means we should appreciate and cherish each of them while we have them, but do so wisely, knowing that one day they will be gone. One day I will no longer have those I love around for me to appreciate; one day I will no longer have all my cherished possessions; one day I will no longer have my life, and will no longer have time to choose the path of salvation. When will these days be? I haven’t the slightest idea.
Yet, while we should appreciate these transitory things, we should never lose sight of He Who alone is not transitory. We must appreciate the transitory things transitoriness, and take care not to make any of them our foundation. God alone can be our true foundation; for He is the one foundation which will never break or cave in.
While I do as of very recently have a skull on my own desk, I’ll admit that it’s nothing from a laboratory … mine’s a rubbery Halloween decoration. But it gets the point across. For that matter, Halloween itself can help to get this point across. I know some Catholics do not celebrate it, and I respect that; but I am one of those who do. And I think that, if one remembers the true meaning of All Saints’ Day (which is tomorrow—and which, by the way, is a Holy Day of Obligation), and looks a little deeper than the surface appearance of the five-year-old Grim Reapers and little rubbery skulls, he will be reminded of the death that constantly stalks him and all that he knows of the physical world around him—the same death that overtook both the uncanonized souls (who we hope were well prepared for it) and the saints (who we know were well prepared for it). And what a crucial reminder that is.
A similarly important reminder is that which it gives us of sin, the cause of death. An/the original purpose of Jack-O’-Lanterns, for instance, was (to my understanding) to use them to scare away evil spirits. Ridiculous as that sounds, it can remind us of such spirits’ (i.e., demons’) very real existence—and, if we think about it enough, of their state of separation from God, something we want to take care not to share in. And of course, it also mocks them—wouldn’t you be insulted if someone thought he could scare you with a pumpkin?—something demons can’t stand: http://www.theimaginativeconservative.org/2015/02/laughing-lucifer-lewis.html
This is what’s important to remember, then, when celebrating Halloween: in being “spooked” by things, we should remember why we’re spooked—out of fear of death and evil, both very real things which we should not fail to forget the existence of. If we keep this sort of thing in mind, along with Christ’s victory over sin and death** and take care to have a God-centered, non-evil celebration ourselves, there should be no issue with celebrating a spooky Halloween.
*I’ll admit that I’m inspired in part here by the line “One day, you’ll leave this world behind/ So live a life you will remember” in Avicii’s “The Nights.”
**The first article linked mentions part of this in regard to keeping a skull on one’s desk. A Word on Fire article about Halloween I think also mentioned this, I think.