Okay guys I'm a little late to the party, but here's what I think:
I think this song represents Spongebob and Patrick trying to make the most of their life while they still could, and growing old they want to remain happy, viewing Plankton as a worse case scenario to life, he's arrogant, vindictive, and as the song said, "will never be satisfied". Plankton represents what Spongebob and Patrick don't want to become, so they decide to be happier in life, even if it makes them look like a kid.
Okay guys I'm a little late to the party, but here's what I think:
I think this song represents Spongebob and Patrick trying to make the most of their life while they still could, and growing old they want to remain happy, viewing Plankton as a worse case scenario to life, he's arrogant, vindictive, and as the song said, "will never be satisfied". Plankton represents what Spongebob and Patrick don't want to become, so they decide to be happier in life, even if it makes them look like a kid.