You are mixing two different terms here: The blockchain is a list of transactions that are linked to each other using cryptographic functions. Each block in the chain links to it's parent block. The genesis block is the first block created, it has no parent block. As proof that Bitcoin wasn't started before a specific date, the block references a The Times headline ("Chancellor on brink of second bailout for banks").
Dan Kaminsky figured out a way to embed ascii text into the block chain. I did not try to find out how he did it, but he probably created some transactions that include those strings. If you want to find out more about how he did it, he will give a talk at the Chaois Communications Camp related to Bitcoin.
Edit: corrected for improper terminology. I understand now.