He pumped out 489 separate designs for St. Patrick's Day. One of his tactics was targeting different Irish last names with personalized campaigns, such as one for "Gallagher."
Targeting last names was a common method used by early Teespring pioneers, though the effectiveness of it has diminished over time, as copycat sellers have crashed into the market. The art of making a Teespring hit usually isn't about any particular cleverness, but rather about finding a specific market and then throwing wave after wave of designs at it.