What's happening to this little plant?

I can't get that picture to load, could you add it to your post as an image instead of a link? If you hit the quick reply link, the picture button is the little square with kind of a landscape in it.

 

Usually the first leaves are a set of two opposite leaves. You seem to have three. They look a bit deformed, as if something was in their way when they were growing. There should be new leaves emerging from the center but I can't tell. Your picture is very large, but blurry. Actually, too large and too blurry. Try to get a shot in better focus, and reduce the size so that it can load quickly for us.

I'll bet your coffee mug has no drain holes. Forget about scenic beauty and put it in a container with holes in it. Better yet, start a new seed and see how it grows. (I'm assuming it's bag seed 'cause you said "shits and giggles".) Maybe this one is just a mutant, or maybe it's suffering and should be put out of its misery.

 

Forgot to say the MG soil prolly has nutes pre-mixed in it. If your soil is always moist, these nutes will continually dissolve, resulting in too much nitrogen in the soil. This could be the cause of the dark green color. Also, your closet may be too hot if you have no ventilation.

 

1. Add a fan and get some fresh air to that guy. Air strengthens them.
2. Give them more light. They need more then just one "energy saving bulb".
Get 2 25watt cfls and you should be set. You shouldnt need anything fancy.
3. Dont overwater them. Thats probably the number one mistake most new growers do.
Their roots need to breathe too.

 

That's some weird shit... where'd you germinate that thing, a microwave?

Leaves shouldn't split to form more... but sometimes the first couple sets of leaves can be deformed and that can happen. Just let it go and try not to over water and see what the new growth looks like...

-Loki