Knock, knock.
Who's there?
Island.
Island who?
Island the one that knows you!
Island Who?
Explanation
Explain Bear
Listen here, buddy. This is a play on words. "Island" sounds like "I land." The last line of the joke, "Island the one that knows you!" is supposed to sound like "I'm the one that knows you!" The joke is, this joke writer thinks he's so smart. But here you are, struggling to figure it out. Sad!