When any extroverts out there can tear themselves away from the party they're currently attending (

), please take a moment to explain how you experience extroversion.
Heheh... we could start by dispelling the "all extraverts have millions of friends and are constantly invited to great parties where they're the life and soul" myth... hehe...
Pretty much everything that happens around me. Anything from a person walking into the room, to a painting on a wall. I wouldn't say everything stimulates me an equal amount, by any means. A fun, pleasant conversation with like minded friends over a pint and a pub lunch leaves me feeling invincible. A phone conversation with someone I haven't seen for a while, who carries their side of it well and has plenty to say, can give me the energy to say, wash the dishes.
But just standing/sitting in a room where lots of people are and things are happening makes me feel a strong compulsion to interact. If something prevents me from doing so - if I don't feel incredibly welcome, ill at ease, or perhaps it's a matter of protocol/etiquette, or if I'm just not feeling very confident or able to put my thoughts into words - whatever the reason, if I'm prevented from interacting and just have to sit there observing, it feels like one of the worst scenarios possible for me. I become extremely frustrated and the feeling of pent-up-ness is unbearable. I tend to seek to leave at the earliest possible opportunity and as soon as I'm out of the building I might even literally scream, shout out or run across a parking lot or something, because of the great need to expel the pent-up energy. Woe betide the friend who accosts me in such a mood - they'll be talked to death!!!
How much stimulation do you need?
Quite a lot. Well, it's more a case of variety than quantity. I can't seem to really spend very much time on any one thing before it ceases to stimulate me, and if I have to continue with it after I'm bored with it, it begins to have the opposite effect of making me feel tired and drained. I'd say that on an average day, I'd need to have at least three or four different experiences of interaction with the outside world, to maintain a minimum level of mental energy that it takes to say, be bothered to cook dinner.
As a rule, the longer I'm left still and without stimulation, or in an environment where the stimulation doesn't change sources, the more lethargic and down I get. That's sorta 'most of the time'. But there are days, probably about one in seven, where I need to stay at home and just sit and contemplate, without having to interact with the outside world. If I don't get those, I get very grouchy.
Out of each 24 hours though, say I spend 8 sleeping (no, let's just pretend hahahaha), I'd say I need around 4 to 10 of the remaining hours to contain external interaction. Anything from a trip to the grocery store to a friend or two staying round all evening. But reading a book or watching a good TV show or movie can also count as external stimulation for me. But I still always need a couple of hours to myself before I go to bed.
What is your internal world like?
Pretty rich actually. Though I don't give as much time to it as I do to external stimulation, I do give
just as much priority to meditation each day. At least half an hour in silent reflection with my eyes closed, and at least once a week I need to spend a good 3 hours or so at it. In those times an awful lot of stuff goes through my head, gets turned over, analyzed, dwellt on, y'know... pretty much everything I've seen, heard and experienced gets processed and turned into all sorts of strange and wondrous ideas, thoughts and feelings. I'd say a fair proportion of my inner world time is spent trying to locate, identify and understand my emotions... with little success

But just as much is spent in purging and disciplining them, where they're analyzed and realized as inappropriate or destructive.
Every now and then, I drive to the beach (in all weathers) to just spend several hours gazing out at the sea and listening to it. I couldn't even say what goes through my head when I do that... everything and nothing.
I have rich, complex, dynamic and deep relationships with quite a few people who died a long time before I was born, which were developed in my inner world, in my 'me times', and which provide a reference point or loom upon which my experiences of the world are woven.
What comes along with being an extrovert that most people don't realize?
Pressure. To always be the one that carries everything along while other people passively look to you for leadership, often contributing nothing but dependency. Exhaustion - the physical toll that's taken by the mental demands for stimulation, and the mental toll that's taken by having to repress your own needs to lead and draw out others.
And ill health - when you feel tired and need to rest, but a person unexpectedly calls and the energy that comes from the stimulation of their presence instantly fools you into thinking you're not tired or ill any more, so you push yourself beyond the boundaries of physical endurance all the time. Kinda like a copier that's been running too long, printed too many copies so it's all overheated inside... if you keep putting paper in it then it'll just keep on copying and copying until it gets so hot it explodes... people need to be sensitive to when extraverts are tired or ill, and take the initiative of leaving us alone so we can rest, because it's highly unlikely that we'll realize we need it when you're around, let alone ask you to leave.
You may return to your regularly scheduled extroverted activities.
I wouldn't say much is regularly scheduled in a typical ENTP's life
I'd also say that I relate to what niffer said as well, except that whilst being completely immersed in the dynamic of the group, I'm also strangely detached from it... which I think is the difference between Ne/Fi and Ne/Ti.