The Flash is an action packed show, and since the main protagonist's power source is speed itself, it stands to reason that people might not catch everything that flys by the screen.
Maybe that's the reason viewers have yet to catch on to an ongoing easter egg. Flash actor Grant Gustin was recently asked if he had stashed any hidden items on the set, and it was here that he revealed a special easter egg that the cast has worked into every episode since season one (via TV Insider).
"No, not personal items, but no one seems to notice that we have a rubber duck that we’ve fit into almost every single scene in the police station. We have been doing it since early in Season 1. Sometimes it’s in an evidence bag that a cop is carrying."
The Flash is just about to start its third season, and aside from the return of the rubber ducky, the show will also see the debut of a costumed Wally West and a focus on the Flashpoint storyline from the comics. The stage was set during the season two finale, where Barry made the choice to save his mom. Gustin was asked about how much trouble that gets Barry into as we enter season three.
"I’m going to sit down with the writers [this summer] so I have an idea, but at this point I’ve tried not to think about it too much. I’m scared to find out! The beginning of Season 3 is going to be rough."
The Flash returns to The CW on Tuesday, October 4th.