I've had tons of Alien dreams.
Probably the worst dreams I've had though involve Yetis.
The first one: Me, my older brother and my sister (as well as some big hunter-type guys) are all walking through these woods in the mountains at twilight. We know the Yeti's/Bigfoots are watching us because we keep hearing things off in the distance. It's all like a cross between Blair Witch and the wood-chase scene from Dog-Soldier (but this is before I saw either of those films BTW). We happen across this log-cabin that's maybe 10ft x 10ft x 8ft and notice these ****ing huge chunks that've been torn from the roof and we're like "Uh, yeti claw-marks". But it's getting really dark and the Yeti's are getting closer so a few of us go inside and barricade the door and some of the hunter guys wait outside next-to the door and on the roof with guns. Someone then mentions that one of the hunters might have shot a baby-yeti eariler that day so there looks like there's no chance of the yeti's just leaving.
After a few minutes we hear gun-shots and screams then the shack starts shaking as the yetis attack it. My brother and sister try to pull the bracing-ropes and hold the shack together while I keep a gun handy. Eventually the shaking stops and we venture outside where there's like 2 hunter-guys left alive and covered in yeti-blood. We decide it's probably not a good idea to be hanging around for another night and head down the the nearby river as the sun rises. The hunter-guys build a little log-raft and we all set off down the river. A coupla minutes into it and we can hear things moving in the bushes off aways at the banks of the little river. Now, the bushes are only like 3ft away but being a dream this fact doesn't matter much. Slowly the landscape turns to a snowy-mountain kinda deal with bits of ice floating in the water. I lean over the edge of the raft to take a look at the ice and see this grey blob about 20ft deep in this 2ft deep river. It approaches fast and soon I'm deafened by a screeching sound as a Yeti lunges up out of the water and drags me under to my death.
Then the dream cuts to a kinda news-report thing with police fishing things outta the river in the background and news-teams swarming the area. The dream ends with a female chinese reporter, cloaked in black, holding a microphone and looking into the camera and saying "Today, a terrible tradgedy befell this quite mountain area. A group of explorers and hunters searching for, and in some cases trying to destroy, the legendary bigfoot met their gruesome end. No-one is quite sure what happened to them, but in this reporters opinion, nature took its course and these proud few were killed by the very thing they sought to destroy..........."
And this is why I'm now scared of Gorillas.
The other one involves an invisible yeti trying to get into my house and kill everyone and me deciding I'm not gonna be terrorized by some pussy-ass monkey and trying to attack it with a door and then a huge knife.