I discovered My Little Pony thanks to cracked.com.
They had an article discussing the four fads way outside target
demographics.  One of them just happened to be My Little Pony.  They
stated that for some reason this show had a major attraction for males
ages 16 to 30. 

(I have a few thoughts on this below.)

Now I, for one, have been
no stranger to girly shows in the past. (And am a lover of a good
cartoon) I have at one time been a huge fan of both sailor moon and
powerpuff girls.  Being the inquisitive and curious person I am I
decided to do some research about this show.  In my research I learned
that Laurent Faust, the wife of Craig McCracken (whom is the creator of
powerpuff girls) was the creative lead behind my little pony, so I
decided to give it a go. I have to admit  what I discovered surprised
me.  After watching the first episode (which was a two parter) I
actually WANTED to watch the next one! 

I will admit I went through some acceptance issues at first.  The
feeling could be compared to figuring out that you enjoy collecting
barbie figurines, or crocheting.  Not that there is anything inherently
wrong with it, but it is deemed “socially inappropriate”.  So now I had
to figure out why I liked it so much.

So why do I like it?  I have several reasons.  From an unbiased
technical aspect, It is well written, often referencing pop
culture(Chocolate Rain, Big Lebowski, Trainspotting, just to name a few)
and it makes me genuinely laugh and smile without the need for crude
childish humor (a feat in itself in my opinion). The show is created
entirely in Adobe flash.  This is a pretty impressive feat.  Especially
when you see how much detail goes in the scenery, in the characters, and
even little details like swaying leaves and the like.  Yes it can be a
bit pastel at times, but for me this just adds to the charm.  The songs
are very catchy.  Listen to winter wrap-up or cutie mark crusaders and
tell me you aren’t humming them for days.

Now  what about the rabid fandom?  What is it about a little girls
show that draws this audience?  For myself personally I think it fills a
void I didn’t know I had.  (Maybe this is true of others as well.)  I’m
not ashamed to admit I wasn’t exactly mister popularity in school.  I
knew a lot of people, and people liked me, but I didn’t have a lot of
social interaction. Even to this day at nearly 30 years old, I spend
most of my time glued to a computer on facebook and other sites rather
than having a so called “social life”.  Now the entire premise of this
show is friendship and helping each other, being there for your
friends.  I think that the lessons presented in this show would have
helped me greatly when I was growing up.  Every episode presents real
world situations disguised in a pony-esque way that would be easy for a
child to digest.

The message of each episode is so positive and uplifting that even
if I am in a terrible mood I will be grinning from ear to ear at the
end. There aren’t a lot of choices for positive uplifting Tv shows other
than veggietales, and if you aren’t a Christian then that show will
have nearly zero appeal.

As if a positive, life lesson teaching show wasn’t enough, then you
have the ponies themselves.  The character development on these
characters is excellent.  There are 6 main(mane) cast that each have
distinct personalities.

Twilight sparkle is a socially awkward bookworm who doesn’t always
know how to react to situations. She is very smart and always turns to
books (and her friends) for guidance. (I associate with her issues
sometimes, personally)

Rainbow Dash, a girl who is just one of the guys.  She is a little
brash, outspoken, a bit rude at times, but is always there when you need
her, loyal to a fault.

Fluttershy is a soft spoken quiet girl,
has difficulty with social situations, but would give her life for her
friends if needed. (I have also associated with her issues of shyness
and social anxiety)

Applejack is a country girl, strong willed and athletic, and
stubborn at times.  She is a great and dependable friend who always
thinks of others before herself.

Rarity is a bit of a diva, prim
and proper, always on the cutting edge of fashion and must always look
her best.  She is very generous and would drive herself into the ground
just to keep her friends happy.

Last but not least, my personal favorite is Pinkie Pie.  This pony
is playful, never angry or hostile.  She loves to smile and laugh.  She
has no shame, and will do whatver it takes to make her friends smile
with her.

I don’t know what it is about these ponies but one of them will
burrow their way into your heart if you are a fan of the show.  (From a
psychological standpoint I would almost say it is the personality type
of the opposite gender that you would be most compatabile with, or
attracted to.)  Most everyone in the community has a favorite.  There is
much good natured ribbing in the community over who is “best pony”. 
Though unlike many other fandoms it rarely ends in flame wars or
trolling.

This brings me to another point.  The community.  This community of
fans is simply amazing.  A recent survey showed over 9000(pun not
intended) “bronies” (gender neutral term for fans of the show) spread
all across the globe.  Bronies are typically good natured, fun loving,
people who like to follow the mantra of “love and tolorate” that is so
present in the show.  They are (usually) pleasent to have discussions
with.  They are also a talented bunch.  The arts, crafts, music, and fan
fiction they create are of a very (almost professional at times) high
calibre.  Song remixes, original compositions, songs (with lyrics),
games, Ive seen it myself, and it is simply amazing.

While there are many sites for the fans of this show to “graze” the
most popular is one called Equestria Daily.  It recently hit 100,000,000
pageviews in about a year.  This site has helped keep the fandom fire
burning strong, as a sort of hub for all the art, music, and etc that is
posted daily.   (There are typically anywhere from 3 to 6 updates a day
every single day!) 

One of the most impressive things in my opinion is the influence of
the fandom over the shows creative staff.  Rather than being repulsed by
the eccentric fanbase (as they maybe should have been), they choose
listen to their suggestions with open minds. 

As an example a “DJ” unicorn featured for only a brief moment in one
episode became a fan favorite and was featured in a commercial spot on
the hub network playing a song remix called equestria girls (a spoof of
Katy perry’s California gurls). At the end of the video a shout out is
given to DJ PON3 (PONTHREE) a name given to her by the fanbase.  An
extended version of this music video was created just for equestria
daily in which the ponies shout out to all their bronies.

An even better example than this was a little background Pegasus.  As a
joke, she was given a lazy eye as the camera pans past.  Fans noticed
this.  Before long they had developed a personality and backstory for
the character, lovingly calling her Derpy Hooves.  The creative team not
only acknowledged this name on the Hub website, but regularly features
her, crazy eyes and all, appearing several times each episode!

Now, I’m not going to deny that there are people who do not have
their shortcomings who watch this show.  There are the Rule 34 crowd,
but honestly, what fandom doesn’t have these folks, you take the good
with the bad!  I think there are some misconceptions about your typical
brony though.  For one, the most common reaction (FAG!) is a little
silly.  From what I’ve seen, most bronies are heterosexual!  There was a
segment  Fox news did on Bronies, that can be found on youtube.  They
compared them to “infantilists” saying that they are quitting their jobs
and drawing welfare to support their “habit”.  Now I personally work a
40 hour a week job, have a wife, and a kid.  I kind of resent the
discrimination based on one or two possible bad apples.  If you look
hard enough, I’m sure you could find these same bad apples in any fandom
of any type in the world, but the few bad ones should not represen the
group as a whole. 

Getting back to the original point though, I’m sure you are still
thinking, “Who cares, tl;dr.  This is still a little girls cartoon.” 
I’m ok with that.  For me, this show is an outlet (and may be for others
as well.).  I personally was encouraged, growing up, to be sensitive,
understanding, caring, and in touch with my feminine side.  I was
allowed to play with barbies and baby dolls.  I know that many males do
not have this option.  Today’s status quo tends to say a man is a man. 
He has to work hard, bring home the money, drink beer, watch sports, get
dirty, and he better as hell know a thing or two about cars.   If he
doesn’t, he’s gay.  No questions.  (I know people who have this mind
set, it drives me insane!)  This show lets you release that pent up
feminine side that I’m willing to be many males have, even if only for a
22 minute episode at a time.  For me, when I watch the show, it’s like
glimpsing paradise if paradise were run by candy colored ponies!