Hi, Marlene!
Fantasmic! is my favorite show in all of WDW, and it's definitely one of those not-to-miss events that I suggest for anyone and everyone. It's a 25-minute show at Disney's Hollywood Studios which features Mickey against almost every known Disney villain and includes many other characters...of course, with a triumphant ending. The show features great special effects including pyro- and hydro-technics and fireworks. The Hollywood Hill Amphitheater -- where Fantasmic! is shown -- can seat almost 7,000 guests with standing room for another 3,000. It's a very popular show which is not shown every night, and for some nights, it is shown twice.
The theater usually opens as much as two hours before the show. However, I recommend designating a "sitter" to reserve seats for your traveling party maybe one hour in advance of the show. Also, I suggest seeing the 2nd show -- if two are offered -- which probably will be the least crowded of the two performances. As with any theater, the best view will be in the center about 1/3 of the way up. If you're too close, you may get sprayed from the water effects.
DHS offers a
Fantasmic! Dinner Package which provides reserved seating 30 minutes before a performance at no extra cost by booking a dinner package with one of three DHS restaurants -- the Hollywood Brown Derby, Mama Melrose's Ristorante Italiano and Hollywood & Vine. You can call 407-WDW-DINE or book it online with your other Advanced Dining Reservations.
Have a wonderful day and a magical vacation!