I was searching for the IKEA heart pillow in the catalog and it was nowhere to be found. I went to a household that has it in order to eyedrop it and I realized it has been "replaced" by a CC item, particularly this one :

Now, I'm no object creator but I'm assuming this isn't supposed to be happening with a simple sculpture object.
The creator states that it has been cloned from the EAxis "The Measure of a Sim" sculpture (I also saw it when that specific EAxis sculpture had a recolour with the texture of the plushie)

Apparently no one has noticed yet or it's a problem of mine and it isn't the CC's fault.
The heart plushie hasn't been totally default replaced. The households that have this still retain the original heart plush, but when I eyedrop it and (maybe, haven't tried it) select it, it shows the CC item. It doesn't behave like a default replacement would. This is what happens when I eyedrop it:

There it is: It selects the plushie and states that it IS the heart pillow.
Now here's the thing: If it's the CC item's fault , would it be safe to remove from the game? Okay, I know there would be blue flashing in the households that I'd had placed the CC item in, I could just remove it from the household again, but I'm talking if it also deletes the heart plush as apparently it has replaced SOME of the item's package info. I'm currently backing up my Sims 2 Documents folder before I do, so I'm just asking here.
Also if this is in the wrong forum, I'm so sorry, please move it.

It's likely that whomever made the pillow didn't give it a unique GUID and therefore it's overwritten the original object it was cloned from. Just take it out of your downloads folder and everything should be fine. To be safe, don't delete it out of the catalogue.

Alright, that's what I was thinking.
I didn't even notice it until now. Though I really don't understand why it would overwrite that specific one as it was cloned from the wooden Sim figure and not the heart pillow, but I guess weird things happen.
Thanks for your help!

You can also designate a new GUID to the object (just remember to fix the GUIDs in the MMATs for the recolors afterward).

You can see exactly what it was cloned from after you remove it. Stuff will usually revert back to the Maxis object when the CC object is removed. That Venus de Milo statue shows up in a lot of houses when I'm testing CC free. XD

I've had items show up ingame alongside the items they were supposed to be "replacing" due to a GUID conflict, but instead they were messing with the MMATs and recoloring the EAxis object instead. Weird one, but still. There's also been the odd object that had its GUID replaced in the OBJD but not in the MMATs, causing the recoloring issue. I had so many strange "recolors" of a couple of the vases people commonly clone. For all I know, it could be caused by the CEP doing a final override, or some such.

I just thought of it requiring IKEA (Correct me if I'm wrong, I'm totally inexperienced when it comes to these things so laugh at me all you want) if it was cloned from the heart pillow thus replacing it, so it's a bit weird.
I removed the object from my downloads folder and the heart plushie went back to normal.
I'll check a household that I placed the CC plushie in and see from which item it was cloned from.
@simmer22 and @Charity , thanks for your help! I appreciate it.

Simple explanation for the issues - the item seems to be tied to two ingame GUIDs:

Main GUID: 0x7520C48A (IKEA heart)
MMAT guid: 0x8CA69957 (wooden Sim model, + fallback GUID)

So it would indeed try to replace the IKEA heart, while trying to recolor the wooden model.

No idea how this combination was achieved just by cloning the wooden sculpture (unless randomly chosen GUID turned out to be not so random, and they forgot to tick the MMAT button + update), but at least it explains the weirdness. Giving the item a completely new GUID and updating the MMAT should make the item properly standalone.

(I've PM'd the creator about the issue).

That explains it! That was strange. Thank you all for helping with this problem.