"Novelty" arcade games were games that did not award replays (free games).  The awarding of replays was illegal in some states as it was considered a form of gambling—the replay was the "payoff."  As a result, manufacturers started producing two versions of the same game, one that awarded replays and one that did not.  For a time, Williams distinguished its baseball replay and novelty games with the word "Deluxe," where the deluxe version awarded replays and the "regular" version did not.  Examples are 1957 Baseball (novelty) and 1957 Deluxe Baseball (replay), Official Baseball (novelty) and Deluxe Official Baseball (replay).

"Add-a-ball" games were pinball machines that appeared in the early 1960s, primarily Gottliebs, that awarded extra balls instead of replays.  Again, this was a way to circumvent the gambling laws of certain states.  The awarding of extra balls and thereby extending the game was legal, while the awarding of complete free games (replays) was not.  Go figure.