Explanations

YOU WOULD NOT BELIEVE YOUR EYES= You wouldn't believe what you see, you'd be very surprised.

FIREFLIE (BrE)= Lighting bug (AmE). A flying insect that glows in the dark (see picture).

LIT UP= (light-lit-lit) To light up means to illuminate a place, but it also means to make or become cheerful or animated. Both ideas fit here.

AS I FELL ASLEEP= When I fell asleep. To fall asleep is the process from being awake to being asleep.

CAUSE= Because.

THE OPEN AIR= The place or space where the air is unenclosed; the outdoors; the outside.

TEARDROPS= A drop of water is a small unit of water, like when it rains (a raindrop). A teardrop is the drop of water that falls from our eyes when we cry.

YOU'D THINK ME RUDE= You will probably think I'm rude.

BUT I'D JUST STAND AND STARE= But (if I saw 10,000 million fireflies) I would simply stand and stare. STARE= To look fixedly, concentrating, almost without blinking (closing your eyes). Children are always told that it is very rude to stare (because if someone stares at you it feels very uncomfortable).

I'D LIKE TO MAKE MYSELF BELIEVE THAT...= I'd like to convince myself of...

PLANET EARTH= Our planet, where we live.

IT'S HARD TO SAY= It's difficult to say.

I'D RATHER STAY AWAKE= I'd prefer to stay awake (not to sleep).
I'D RATHER + infinitive without to = I prefer + infinitive with to:
- I'd rather stay here with you = I prefer to stay here with you.
- I'd rather live in Pisa than in Paris = I'd prefer to live in Pisa than in Paris.
But if I'm referring to another person, not me, it is followed by a past tense.
I'D RATHER + (you, he, John, etc.) + past tense:
- I'd rather you stayed here with me = I prefer that you stay here with me.
- I'd rather he went = I prefer that he goes.

I'D RATHER STAY AWAKE WHEN I'M ASLEEP= This sounds like a contradiction. How can you stay awake if you are sleeping? He simply means that he prefers to have dreams when sleeping (in a dream you are awake) because they are his source of inspiration.

HUG= An embrace, when someone puts their arms around you.

LIGHTNING BUGS (AmE)= Fireflies. (bug = insect)

AS THEY TRIED= When they tried, while they tried.

FOXTROT= An old ballroom dance.

ABOVE= /əbʌv/ Over.

SOCKHOP= (he pronounced /sɒkɒp/ but it should be /sɒkhɒp/).The sock hop was an informal dance at American high schools, typically held in the high school's own gymnasium or cafeteria. The term sock hop came about because dancers were required to remove their shoes to protect the varnished floor of the gymnasium. These hops were a cultural feature of the 1950s and early rock and roll.

BENEATH=/bəni:ð/ Under (the oposite of "above")

A DISCO BALL= A spinning ball covered with little pieces of glass used in discos to send little spots of light everywhere (see picture)

THREAD= A fine strand, filament or fibre of some material. (see picture)

HANGING BY A THREAD=Disco balls are suspended from the ceiling by a thread. Notice the preposition BY used with the verb "to hang".

A DISCO BALL IS JUST HANGING BY A THREAD= The word JUST is often used as an emphasizer (to highlight the word coming afterwards), but it very often means nothing at all, and in songs, it is very often used simply because it easily adds an extra syllable to the sentence wherever it is needed.

JUST A CRACK= Only a little bit. A CRACK is a little narrow space, so if a door or a window is open a crack, it is almost closed, but not entirely (we can also say that it is ajar).

INSOMNIAC= A person who suffers from insomnia, who can't sleep.

I FEEL LIKE SUCH AN INSOMNIAC= I feel that I am a case of serious insomnia, I feel that it's really hard for me to sleep.

TIRE= Get tired. This verb is very formal and old fashioned, in normal English we prefer to use the phrase "get tired" or "be tired".

COUNTING= He pronounces this "couning" because in AmE sometimes N+T=N, so the T may disappear after an N.

I TIRE OF COUNTING SHEEP= I'm tired of counting sheep. (after prepositions and conjunctions we use –ING so: of + counting). The word SHEEP has no plural form (one sheep, two sheep). In this sentence "sheep" is plural.
People who can't sleep typically count sheep in their minds as they jump over a fence because they say that counting sheep is so boring that you finally fall asleep. Psychologists say that counting sheep in your mind helps you sleep because your mind is fixed on a mental image while counting; both your visual and linguistic parts of the brain (left and right hemispheres) are busy, so you can't think of anything else and finally fall asleep (insomniacs usually can't sleep because they can't stop thinking).

FAR TOO TIRED= Much too tired. We can use FAR or MUCH to make a comparison (more) or an excess (too) stronger, for emphasis:
- Kevin can sing far better than me (= much, much better, a lot better, way better)
- That's far too expensive for me (= that's much too expensive)

TO TEN MILLION FIREFLIES...= For them, in their opinion, I'm weird.

WEIRD= /wɪə*d/ Strange.

MISTY= Foggy, covered with light fog. Also, when it's cold outside and warm inside, your window panes may get misty (it looks like it's foggy outside) because of water condensation.

GOT MISTY EYES= I've got misty eyes. If your eyes are misty (like a window pane) there is water condensed there, so you are almost crying, but not yet (your eyes are watery but still no teardrops). When you feel too touched or moved by something but you try not to cry, your eyes get misty.

FAREWELL (old fashioned, poetical)= Goodbye.

BIZARRE= Very strange.

REAL BIZARRE= Very very bizarre. The correct form here should be "really".

JAR= a wide-mouthed container that is usually cylindrical, made of glass and without handles (see picture).

I SAVED A FEW AND I KEEP 'EM IN A JAR= ('em=them) I kept a few fireflies with me and I have them inside a jar so that they can't go away.

SEAM= When you sew two pieces of material together, the seam is the line of junction, the line where both parts are joined (see picture).

BURST= Explode, break suddenly and powerfully.

MY DREAMS ARE BURSTING AT THE SEAMS= This metaphor means that his dreams are closed inside something, but that thing is beginning to break and all those dreams will soon escape and become real.