90s Kid
90s Kid
[Two kids, with very different hair style, are in a playground. A fence is visible in the background, and on the ground appear to be various items including a puddle or rug and toy blocks.] Scruffy-haired kid: Ugh don't you hate how parents are all "Eat your carrots" and "LOL, remember Rugrats and Doug? Share if you're a 90's kid!" [Caption below the panel:] The median age at first birth in the US is 25, which means the typical new mother is now a 90's kid.

This is another example where Randall describes the inexorable passage of time.
The children are complaining about things their parents tell them, as children often do. Their first complaint is something recognizable, the usual "just eat your vegetables, they're good for you." The second is about a comment "LOL, remember Rugrats and Doug? Share if you're a 90's kid" which, however, is a generic social media comment that a "90's kid" would make, not something you would expect a mother to say. At least not in the context of things their children are embarrassed about. But it illustrates that the teens and tweens of yesteryear are now adults, and parents at that.
According to the CIA World Factbook, in the USA the median age of mothers at their first birth is 25.6 (2011 estimate). On the date this comic was published, this would center the mother's own birth date in very late 1989.
Although there are various interpretations of the term "90's kid," most center around the person in question having had most or all of their childhood during the 1990s. The stereotypical '90s kid has a strong attachment to objects, movies, TV shows, phrases etc. from the era of their childhood, which bring back memories of their younger days. In this comic Randall picks up on a number of things which could be used to identify a '90s kid:
Given that the children shown in the comic appear to be somewhat older than newborn babies is not contradictory, since a 90s kid is anyone who was a kid during the '90s. So that would also include kids who turned five in 1990 or even ten; so in 2015 (publishing of this comic) a 90s kid could easily be more than 30 years old and thus have children more than 10 years old.
The title text suggests that viewing a child of one's own peering through such a barrier elicits nostalgia for the Rugrats cartoon. A baby gate is a semi-fixed piece of child-safety equipment to restrict a small child, typically a toddler, from leaving a safe area of a house, and especially to prevent access to stairways (up or down, where falls may happen), without overly inconveniencing an adult who can open the gate. Baby gates, fully enclosed playpens and similar barriers around cots feature as usually insurmountable barriers to the younger characters in Rugrats, who are of crawling and toddling age.
[Two kids, with very different hair style, are in a playground. A fence is visible in the background, and on the ground appear to be various items including a puddle or rug and toy blocks.] Scruffy-haired kid: Ugh don't you hate how parents are all "Eat your carrots" and "LOL, remember Rugrats and Doug? Share if you're a 90's kid!" [Caption below the panel:] The median age at first birth in the US is 25, which means the typical new mother is now a 90's kid.
