In a large bowl, toss together the cereal, oyster crackers, both kinds of Goldfish, and the Melba toast.
In a small bowl, stir together the melted butter, hot sauce, and lemon juice. Pour it over the cereal mix, sprinkle on the Old Bay, and toss until everything is evenly coated.
Spread the mix on a rimmed baking sheet. Bake about 45 minutes, stirring every 15 minutes, until golden and crisp.
Let it cool completely. Store in an airtight container at room temperature for up to 1 week.