It's little Smithers' 9th birthday (because I imagine that March is Waylon's birth-month) and Burns want to celebrate him as he never feel before. A nice, familiar-like and warm party, where everyone is there.
Waylon feel a happiness that he never felt in his own house, but now in his new home.
C. Montgomery Burns and Waylon Smithers Jr. (c) Matt Groening
Helene Dupalais and Winston Feng (c)
Helene and Winston's design (c)