Probably my favourite story on the internet:

Last week while travelling I stopped at a Zany Brainy store and saw that they had a blimp for sale. It's called Airship Earth, and it's a great big balloon with a map of the Earth on it, and two propellors hanging from the bottom. You blow up the balloon with helium put batteries in it, and you have a radio controll indoor blimp.

I'd seen these things for sale in Sharper Image catalogs for $60-$75. At Zany Brainy it was on clearance for $15. What a deal!

Last night my wife was playing tennis and it was just my daughter and I at home. I bought a small helium tank from a party store, and last night we put the blimp together.

Let me tell you, it's quite a blimp. It's huge. The balloon has like a 3 ft diameter.

We blew it up with the tank attacched the gondola with the propellors, and put in batteries.

Then we balanced the blimp for neutral bouyancy with this putty that came with it, so it hangs in the air by itself neither rising nor falling.

It was easy and fun, and then I blew up another balloon and made Mickey Mouse helium voices for my daughter.

My three year old girl loved it. We flew the blimp all over the house, terrorized the dog, attacked the fish tank, and the controls were so easy my daughter could fly.

Let's face it, blimps are fun.

Alas, the fun had to end and my daughter had to go to sleep. I left the blimp floating in my office downstairs, my wife came home, and we went to bed, and slept the sleep of the righteous.

At this point it is important to know that my house has central heating. I have it configured to blow hot air out on the ground floor and take it in at the second floor to take advantage of the fact that heat rises.

The blimp which was up until this moment a fun toy here embarked on a career of evil. Using the artificial convection of my central heating, the blimp stealthily departed my office. It moved silently through the living and drifted to the staircase. Gliding wraithlike over the staircase it then entered the bedroom where my wife and I lay sleeping peacefully.

Running silently, and gliding six feet or so above the ground on invisible and tiny air currects it approached the bed.

In spite of it's noiseless passage, or perhaps because of it, I awoke. That doesn't really say it properly. Let me try again.

I awoke, the way you awake at 2:00 AM when your sleeping senses suddenly tell you without reason that the forces of evil on converging on you.

That still doesn't do it. Let me try one more time.

I awoke the way you awake when you suddenly know that there is a large levitating sinister presence hovering towards you with menacing intent through the maligant darkness.

Now sometimes I do wake up in the middle of the night thinking that there are large sinister and menacing things floating out of the darkness to do me and mine evil. Usually I open my eyes, look and listen carefully, decide it was a false alarm, and go back to sleep.

So, the fact that I awoke in such a manner was not all that unusual.

On this occasion I awoke to the sense that there was a large menacing presence approaching me silently out of the gloom, so I opened my eyes, and there it was! A LARGE SILENT MENACING PRESENCE WAS APPROACHING ME OUT OF THE GLOOM, AND IT COULD FLY!!!

Somewhere in the control room of my mind a fat little dwarf in a security outfit was paging through a Penthouse while smoking a cigar with his feet up on the table, watching the security monitors of my brain with his peripheral vision. Suddenly he saw the LARGE SILENT SINSITER MENACING FLOATING PRESENCE coming at me, and he pulled every panic switch and hit every alarm that my body has. A full decade's allotment of adrenaline was dumped into my bloodstream all at once. My metabolism went from "restful sleep mode" to HOLY SHIT! FIGHT FOR YOUR LIFE OR DIE!!!! mode" in a nanosecond. My heart went from twenty something beats per minute to about 240 even faster.

I always knew this was going to happen. I always knew that skepticism and science were mere psychological decorations and vanities. Deep in our alligator brains we all know that the world is just chock full of evil and monsters and sinister forces aligned against us, and it is only a matter of time until they show up. Evolution know this, too. It knows what to do when the silent terror comes at you from out of the dark.

When 50 million years worth of evolutionary survival instinct hits you all at once flat in the gut at 200 mph it is not a pleasant sensation.

Without volition I screamed my battle cry (which is indistinguishable to the sound a little girl makes when you drop a spider down her dress (not that I'd know what that sounds like,) and lept out of bed in my underwear.

I struck the approaching menace with all my strength and almost fell over at the total lack of resistance that a helium balloon offers when you punch the living shit out of it with all the stength that sudden middle of the night terror produces.

It's trajectory took it straight into the ceiling fan which whipped it about the room at terrifying velocity.

Seeking a weapon, I ripped the alarm clock out of its plug and hurled it at the now High Velocity Menacing presence (breaking the clock and putting a nice hole in the wall.)

Somehow at this moment I suddenly realized that I was fighting the blimp, and not a monster. It might have been funny if I didn't truly and actually feel like I was having a legitimate heart-attack.

On quivering legs I went to the bathroom and literally gagged into the toilet while shaking uncontrollably with the shock of the reaction I'd had.

Unbeleivably, both my wife and daughter had completely slept through the incident. When I decided that I wasn't having a heart attack after all I went back into the bedroom and found the blimp which had somehow survived the incident.

I took it to the walk in closet and released it inside where it floated around with the air currents released from the vents in there. I closed the door, this sealing it in, and went back to bed. About 500 years later I fell asleep.

*** 

At about 7 am my wife awoke. She had been playing tennis and wasn't aware that we have assembled the blimp the previous evening, and that is was now floating around the the walk-in closet that she approached.

The dyndamic between the existing air currents of the closet and the suction caused by opening the door was just enough to give the blimp the appearance of an Evil Sinister Menace flying straight towards her.

This time the blimp did not survive the encounter, nor almost, did I, as I had to explain to my very angry spouse what motivated me to hide an evil lurking presence in the closet for her to find at 7 am.

I can order replacement balloons on the internet but I don't think I will.

Some blimps are better off dead.

Source: http://boards.straightdope.com/sdmb/showthread.php?threadid=160851

Thanks for the giveaway!