Actually she mentioned both, showstoppers and 11 o'clock numbers, which sometimes are the same numbers, but not always. If you want the showstoppers, as in the big audience-response numbers from the shows...
Beauty and the Beast - Be Our Guest
Hairspray - You Can't Stop the Beat (or Timeless to Me)
Urinetown - Run, Freedom, Run
Producers - Springtime For Hitler
Chicago - All That Jazz
Cabaret - Cabaret (or Money Money)
Aida - The Gods Love Nubia (or Written in the Stars)
Gypsy - Rose's Turn
Les Mis - One Day More (or On My Own)
Little Shop of Horrors - Suddenly Seymore
Wonderful Town - Swing!
Fiddler on the Roof - If I Were a Rich Man (or Tradition)
Boy From Oz - Once Before I Go
Avenue Q - Fine, Fine Line
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian