In Big City Greens, one of the inside jokes the crew decided to do is insert an "Easter egg" into every episode. An Easter egg refers to an unexpected or unnoticed feature found in media, while in this case, it takes the form of a literal blue egg with yellow polka dots and pink and yellow stripes.
The eggs can be found in one scene of every episode (except "Present Tense" and "Hurt Bike"), usually in hard-to-see places. All of the shots featuring the hidden eggs are listed here.