In Flash #165 (Nov 1966), Barry Allen and Iris West finally get married. This was not DC's first wedding; Aquaman and Mera had finally tied the knot in Aquaman #18 (Nov-Dec 1964), Hawkman and Hawkgirl had been married when they arrived on Earth, and Ralph and Sue Dibney were wed immediately before the Elongated Man story in Detective #327 (May 1964). Reed Richards and Sue Storm over at Marvel had also married in Fantastic Four Annual #3 (1965).
But this wedding was different because it was the first time a superhero had gotten married without his wife knowing his double identity. This created some additional tension for the Scarlet Speedster:
So for the next year we would periodically see Barry musing his dilemma.
Ironically, this point had supposedly been settled before in Flash #156. An alien had arrived on Earth, letting everybody know that Barry Allen was the Flash. But at the end Barry has a chance to go backwards in time and change that memory. But he asks Iris for permission:
Despite that pledge, he finally decides to do the big reveal on their first anniversary. Of course there are only two real ways to go with this kind of moment from a plotting perspective, and DC chose the more amusing one:
The story (as it happens) was also Carmine Infantino's swan song on the Flash, so this is an especially poignant moment.