Customer Appreciation Day is an annual event that the Candy Store runs, where they give out free jawbreakers. In "Don't Rain on My Ed," the Eds find out about this event, but there were only about ten minutes left before the Candy Store closed at that point. The Eds faced many dangerous obstacles along the way to the store, and thus were not able to enter the store before it closed.
This event also took place in the The Mis-Edventures game during the first half of the level "Must Be Something I Ed." There, the Eds do make it to the candy store, however the store was giving out foot-powder flavored jawbreakers, which Eddy was allergic to; they turned his face a greenish color with peach spots. This was central to the second half of the level, as you had to get Eddy home before any of the kids see him. That level largely resembled the plot of "X Marks the Ed," especially the end where the kids caught him and took photos of his embarrassing condition.