December 21 is the 355th day of the year (356th in leap years) in the Gregorian calendar. There are 10 days remaining.
- 2001: "Christmas Who? premiered in Canada.
- 2005: "Christmas Who?" premiered in the UK.
- 2012: "It's a SpongeBob Christmas!" premiered in Indonesia.
- 2011: Pauli Virta passed away.
- 2014: A sneak-peak for The SpongeBob Movie: Sponge Out of Water aired on Nickelodeon.
- 2016: "Pineapple Invasion" and "Salsa Imbecilicus" premiered in Italy.
- 2017: "Don't Wake Patrick" premiered in Germany only with the original English version.
- 2018: "Goons on the Moon" premiered in Greece, Norway, Sweden, and South Korea.
- December 21 on Wikipedia
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