My daughters and I were watching a National Geographic show recently about how the brain works, and I was reminded that memory—human memory anyway—is a finite resource. Each experience, face, and fact that we commit to memory leaves that much less room for something else.

I’m probably not alone in feeling that my house, my inbox, my calendar—my entire life, really—is greatly in need of de-cluttering, and it got me thinking about some of the stuff that’s taking up space in my brain. Family memories. The movies, books, and music that mean the most to me. And…a whole lot of television commercials, many of them decades old.

I wondered: Which commercials are still sticking around in my head, and why?

Here are five that I’m probably stuck with forever—whether I like it or not.

Tootsie Pop—“How Many Licks?”

As someone who has only recently graduated from being the parent of a preschooler, I’ve seen Tootsie Pops stuck to just about everything. But nothing about Tootsie Pops—not even the Tootsie Roll center—has stuck to me as hard as this commercial, which first aired, according to Tootsie Roll, in 1970.

According to iSpot.tv, which tracks real-time TV ad analytics, the 15-second version of this classic commercial aired as recently as November of 2016—nearly 50 years later. That’s getting your money’s worth out of your marketing.

I’m partial to the 30-second version, especially the turtle with the “toothless” mouth lines who claims: “I never made it without biting,” and the time-lapse animation of the licked and bitten Tootsie Pops at the end of the spot.

Some great sticking points in this commercial: the nod to ancient fables, the unexpected humor of the pompous, greedy owl.

But above all of those, the question itself: How many licks does it take? I think most of us, at one time or another, have tried to find out. Tootsie Roll Industries, recognizing that it has a good thing going, still offers a “Clean Stick Award” to those who write with the answer.

Reese’s Peanut Butter Cups – “Two Great Tastes”

It seems as though some variation of this commercial ran pretty much every Saturday morning for much of the 1970s and ‘80s, so it’s not surprising that their tagline from that time, “Two Great Tastes That Taste Great Together,” should be forever a part of my psyche.

The line has stuck with many other people, too, if a Google search of the phrase is any guide. Buproprion and Diazepam. ColdFusion and Node.JS. Fair Use and Open Access. All are apparently great tastes that taste great together.

The slogan has an alliterative symmetry (T.G.T.T.T.G.T.) that nicely mirrors the concept: chocolate and peanut butter are two equally superior tastes that add up to more than the sum of their parts. But it wasn’t the slogan that cemented the TV ads for me, as much as it was the central conceit of having two people—one carrying a chocolate bar and the other eating directly from a jar of peanut butter—collide with one another to make this seemingly amazing discovery.

NOTE: If I were to go around in public snacking from a whole jar of peanut butter, I’m pretty sure I would be inviting some kind of intervention.

Volkswagen—“Milky Way” (aka Pink Moon)

This 1999 TV commercial for the VW Cabrio was conceived using the song “Under the Milky Way” by The Church—hence the commercial’s title. But the list of songs under consideration was expanded and Nick Drake’s 1972 song “Pink Moon” was ultimately the one chosen, a decision that ended up contributing to a resurgence in the late singer’s popularity.

Like a lot of people too young to know Nick Drake’s music from the original releases, I eventually went out and bought a copy of the album that contained the song. Did this commercial sell as many Cabrios as it did Nick Drake albums? That’s unclear. But it seems to have done good things for the larger VW brand.

It also signaled that attitudes over the use of popular music in advertising had really softened. Whereas, a decade earlier, Nike’s “Revolution” commercial had created controversy over its use of a Beatles song (without the band’s authorization), “Milky Way” seemed to mark a time when advertising was becoming a conduit for musical culture, rather than simply an exploiter of it.

But this ad is about more than a great song. It hangs back and allows the viewer to experience the story and the feelings in a way that most commercials don’t. From the opening, with the camera flying up along the moonlit river, to the tight shot on the back of the car as the single backup light comes on, this one truly sells the experience over the product.

Big Red Gum Commercials

Turning from the better to the worse, my research shows that the Big Red Gum jingle was used for almost 20 years, from 1979 to as recently as 1998—even as the growing use of pop songs in commercials was on the verge of driving the jingle into obscurity. Putting “Milky Way” and this Big Red spot side-by-side, it’s not hard to see why.

Still, the Big Red commercials got their big idea across: namely that Big Red kept your breath cinnamon-fresh for lip-locks of such extreme duration that you’d miss your boat, bus, troop transport, hot air balloon, or even your car being towed.

Brim Decaffeinated Coffee Commercials

This commercial—or one of its many variations—plays in my head each time I pour myself a half cup of coffee. It doesn’t matter whether it’s by choice. It happens even at those times when there’s only a little coffee left in the pot.

I’m not entirely sure why this one has stuck with me for so long. It’s partly the rhyme in the tagline. It’s partly—as with the Big Red Gum and the Reese’s Peanut Butter Cup commercials—the repetition of seeing it so many times, in so many variants, each ostensibly different but in fact exactly the same.

I was also just a kid when these commercials ran, and I remember being drawn in by the scenario—cheesy as it was. The idea of someone “liking” or “not liking” someone else’s coffee. The drama of the recovering caffeine addict suffering in self-deprivation, only to be released from his monk-like discipline by the miracle of Brim Decaffeinated.

Fill it to the rim, indeed.