First musical i saw was HELLO DOLLY starring at the time Ethel Merman. For some reason, i have an indelible memory of what she looked like doing the line "Bridge that gap fellas, find me an empty lap, fellas." Almost did it as if whispering, cocking her body as if telling the waiters a secret. but that stage whisper rang out clarion-like to the rear mezz where we sat. Can't explain it well, but it was a lovely intro to the excitement of the stage.
First play was interestingly enough FOUR ON A GARDEN, starring Carol Channing and Sid Caesar. My father managed to get ninth row orchestra seats for this, and Art Carney and Sheila MacRae were in the audience, and were SO gracious about giving autographs. The show was a series of playlets, and only one of them was really good IIRC, but it was loads of fun being there.