I started a new game. I immediately had two missions available: a T flag mission, and a solid circle mission. Did the T mission; I assume that's tutorial. Figured I'd try the solid circle mission.

What is this?? It talks about Ug the Barbarian, but anything I can find on google says he's from secret missions in later levels. This level I have access to has 3 enemy keepers and invading dwarves. All I get are imps and the lightening spell, and no idea wtf I'm supposed to do.

Can anyone tell me what's going on? I do /not/ remember this.

I cannot explain why it mentions Ug the Barbarian, but everything else you describe matches Secret Level 6: Full Moon. This level is offered if your system clock indicates the day of a full moon in the real world. Otherwise, this level is hidden.

That's it! Thank you very much! It was driving me crazy, as I'd never seen that in all the times I'd played DK.

But yeah, it said something about Ug and that he'd be help later if I freed him or something. Which, as I said, is something that I discovered is associated with other secret levels - which is part of what was making it so hard to figure out.

Mystery solved (mostly)! Thanks again!

For what it is worth, the Wiki says that the game will refer to Ug the Barbarian, but the level where you actually encounter Ug instead has Ug the Priestess. I cannot confirm whether that is the case, but if it is, then it would be at least one place where the in-game text is factually wrong. If so, that would call into question whether the message you saw about Ug in this level is also an error in the game as shipped.

All the secret levels were pushed out untested. There's a secret level you can't access, a secret level you can't transfer the unit and the strings are all wrong too. The imp-killing level gives you a vampire but the objective says you get 2 mistresses.

Keep in mind all the in game strings had to be translated, for the objectives and the GUI itself, and these had to be send out a while before development was complete. As such, the texts represent an older, never released version of the game. The tool tip for the cave-in spell still says it can be used to make walls and bridges for example. There's lots more like that.