December 4, 1999 (The final appearance of Spike's cactus)
December 5, 1999 (The last interaction between Linus and Sally)
December 6, 1999
December 7, 1999 (A possible fourth-wall break by Snoopy)
December 8, 1999
December 9, 1999
December 10, 1999 (This strip is adapted in I Want a Dog for Christmas, Charlie Brown and used on the page for August 29 of the Dayspring Peanuts A Year's Worth of Smiles and Blessings Desk Calendar)
December 11, 1999
December 12, 1999 (The last interaction between Lucy and Rerun, and her last speaking role)
December 13, 1999 (The final appearance of Lucy, and the final appearance of Snoopy as Santa Claus)
December 14, 1999 (The day that Charles M. Schulz announced his retirement)
December 22, 1999 (This strip is used on the page for December 3 of the Dayspring Peanuts A Year's Worth of Smiles and Blessings Desk Calendar)
December 23, 1999
December 24, 1999 (The last Christmas-themed comic strip, and the last cold cereal joke)
December 25, 1999
December 26, 1999
December 27, 1999 (The final baseball-themed strip. This was one of several strips shown on display at a Peanuts exhibit at the National Baseball Hall of Fame in Cooperstown, New York.)
December 28, 1999 (The last interaction between Sally and Snoopy, and the last time Sally writes to her grandmother)