My advisor invited me over for dinner tonight.
He wrote the book on nonlinear PDE techniques in the global theory for general relativity.
Around the table were also I. M. Sigal, who wrote the book on spectral theory and applications to Schroedinger equations, and Neil Trudinger, who wrote the book on partial differential equations.
And then there were Joachim Krieger, one of my advisor's former students, and me.