Year 1999 (MCMXCIX) was a common year of the Gregorian calendar that started on a Friday.
- May 1 - Help Wanted, Reef Blower, and Tea at the Treedome, the pilot episodes, premiered, thus starting the series.
- July 17 - Bubblestand and Ripped Pants premiered.
- July 31 - Jellyfishing and Plankton! premiered.
- August 7 - Naughty Nautical Neighbors and Suds premiered.
- October 2 - The Chaperone and Employee of the Month premiered.
- October 28 - Scaredy Pants and I Was a Teenage Gary premiered.
- August 14 - Pizza Delivery and Home Sweet Pineapple premiered.
- August 21 - MermaidMan and BarnacleBoy and Reef Blower premiered.
- August 28 - Hall Monitor and Jellyfish Jam premiered.
- September 4 - Sandy's Rocket and Nature Pants premiered.
- December 31 - Suds and Karate Choppers premiered.