I would assume pasting a node from a different file might happen if it is in the cache, but I just turned the computer on, and opened a new file I just made today. I cut a Curve to paste it in a geometry SOP and a curve I was working on a couple weeks ago popped up?! I am a new user, so I am not sure the issue, though I am thinking it got cooked into some super secret Houdini cache. Anyone know what this is about?

Yep, Houdini does that. Each context can contain only a copied node set from that context. So you may have copied at the object level, went into the SOP level and pasted. But the item on the clipboard at the SOP level happened to be something you copied a while back.

Instead of cutting your curve, dive inside and select the curve node inside the curve object and cut there.

Just brainstorming…

Gracias!

It's not a super secret houdini cache

Houdini stores node clipboards in the temp folder of your system as .cpio files for each context.
SOP_copy.cpio; OBJ_copy.cpio ; VOP_copy.cpio ; FUSE_copy.cpio ; ROP_copy.cpio ; SHOP_copy.cpio ; CHOP_copy.cpio ; COP2_copy.cpio ; DOP_copy.cpio

This allows you to copy from one Houdini session to another or keep the clipboard during restarts like in your case.

With this in mind you can build some nice tools around that and “share” your clipboards with other artists in the company for example.