In "Suds", the man taking a shower during the live-action "sponge treatment" scenes is Tom Kenny, the voice actor for SpongeBob.
Visiting editor/scriptwriter Kairabo Jihaka came up with the sponge treatment sequence in "Suds" after seeing the live-action hand in the intro. When the crew were discussing how SpongeBob should be cured by getting cleaned, she suggested that they use the hand to clean SpongeBob, and entirely in live-action. She also directed Tom Kenny (who was sick at the time of recording) to "sneeze like you're screaming your head off" at the scene where the Krusty Krab explodes from one of SpongeBob's sneezes, "we don't care if you flub it, just do it, he wants to go Super Saiyan."
In "Suds" SpongeBob gets sent home sick but in "The Splinter" segment of The Splinter/Slide Whistle Stooges (2008) he gets hurt and does not get sent home.
In Gary's dream, Talking Gary tries explaining the concept of dreams to SpongeBob by reading the Emily Dickinson poem that starts with, "Let me not mar that perfect dream..."
Although This Episode Premiered In 2000 It Was Made In 1999 According To The Credits