Clumsy- What they did was Young Josh was at the "Zoltar Speaks" machine, wished he was big and Zoltar sang in a booming voice "You're wish is granted! GRANTED!!!!!" and then it cut to black, a few seconds later the lights went up on Josh's house and Adult Josh got out of bed, eventually singing "This Isn't Me".
I saw it, too. I remember really loving it (I was about 7) and running down the aisle during the curtain call in order to catch one of the flying airplanes. It's got a pretty terrific score: Dancing All the Time, Stop Time, Fun, Cross the Line, Stars Stars Stars, and the opening number are all great. The book is not the strongest, but it's pretty solid and never drags. It's a fun show and definitely does not deserve the bad reputation it got after Broadway.
One problem looking back was that the show was WAY over produced. It's one thing to have FAO Schwartz look like Oz, but such things as the street they lived on, the supposed 2nd rate carnival, and Josh's loft were all given the "elaborate, bigger is better, shinier is cooler" look. I recall for the set design with the neighborhood, there were four two floor houses that slid onstage for the opening number, three of which were never used again. There were many things about the physical production that could have been cut, cutting down its production budget and running costs.
it also came out in a year when innovative and new was the thing to be. Think about, Rent and Bring in Da Noise were the two big hits of the new musicals, and the bare bones production of Chicago reinvented how to present a musical. Big was an extravagant musical that didn't break any ground. But it was fun and had a lot of heart and had some great performances (Daniel Jenkins was not nominated for a Tony for some God forsaken reason). it really is a fun show, though. You should be happy you're doing it.
"Sing the words, Patti!!!!" Stephen Sondheim to Patti LuPone.