Greg Walker was a writer for Smallville. Some episodes he has written are:
- Hothead (directed by Greg Beeman) - Coach Walt Arnold is obsessed with winning. Meteor rocks in his sauna have given him the power to cause objects to burst into flames. Clark Kent defies his father and joins the football team. Lana Lang defies expectations, quits cheerleading, and waits tables. Lex Luthor defies his father in a business plan that saves several people their jobs. The coach attacks the principal, a player, and a journalist before Clark stops him.
- Nicodemus (directed by James Marshall) - Steven Hamilton uses meteor fragments to bring the Nicodemus flower back from extinction. It infects James Beels, Jonathan Kent, Lana Lang and Pete Ross before Lex's doctors find a cure.
- Obscura, (co-written with Michael Green and Mark Verheiden, and directed by Terrence O'Hara) - Chloe is kidnapped and Lana is having visions of her attacker. Meanwhile, Lex finds a piece of the ship in Miller's Field and Clark asks Chloe to the spring formal.