holes
Explanation
This comic is a joke about game theory applied to billiards (pool).
A character with big curly hair stands at what is presumably a pool table and declares: "This game sucks. There's an obvious dominant strategy of 'put the balls in the holes in the right order.'" The other players look unimpressed and annoyed.
The caption reads: "Never invite a game theorist to play pool."
The humor comes from the clash between game theory terminology and the reality of playing pool. In game theory, a "dominant strategy" is a course of action that is optimal regardless of what your opponent does. The game theorist character reduces pool to its most abstract description -- you put balls into holes in a specific order -- and declares it trivially solved, as if the strategy is obvious and the game therefore uninteresting.
The joke is that knowing the optimal strategy ("put the balls in the holes in the right order") is completely useless without the physical skill to execute it. Pool is not a game of strategic complexity but of physical dexterity, precision, and spatial reasoning. The game theorist's complaint is technically correct in the most unhelpful way possible -- yes, the goal is to put the balls in the holes, but the entire challenge of the game is the execution, not the strategy. This is a common comedic trope in SMBC: an academic or intellectual character applies their specialized framework to an everyday situation where it is hilariously irrelevant.