Born on the same day as Maggie Simpson, the sub-par Springfield General Hospital had only one diaper left, and it was, of course, given to Maggie. Baby Gerald was wrapped in the discount section of the Springfield Shopper. Because of this, Gerald developed a terrible rash which still persists to this day. He blames Maggie for this uncomfortable condition and spends his nap times plotting revenge.
On a few occasions, Gerald has been shown being pushed in a stroller by his mother outside the Simpsons’s house, with the two babies glaring at each other, the camera focusing on their narrowed stares. Homer often mistakes Maggie for Baby Gerald.Gerald apparently has a history of causing large scale public incidents and was once rescued from an unspecified disaster by Bart’s mail order “wonder dog” Laddie. Both dog and baby were participants in a ceremony presided over by Mayor Quimby, during which the mayor inquired, "Baby Gerald, we can't help but wonder what mischief you'll get into next."
Gerald is a baby who is the same age as Maggie. He has a wide black uni-brow (his main distinctive feature), a big wide nose, an overbite, two buck teeth (that are shown even when his mouth is closed), a blonde curly strand of hair on his forehead, and a couple of curly neck hairs (which look the same as his forehead hair). He usually wears a baby-blue onesie with a light blue bonnet.
FutureIt is revealed that Maggie and Baby Gerald stopped being enemies and eventually got married. The marriage, however, was rocky and it is not clear if he is the father of Margaret "Maggie", Jr. 
In part 21 of "the End of the Beginning" story-arc in The Simpsons: Tapped Out, it's revealed upon rebooting R.O.S.A. that Gerald Samson was the reason why the Springfield Nuclear Power Plant underwent a meltdown seen in the opening for the game in the first place, as Gerald, in a tantrum due to being denied a donut due to being put in time out and thus not being "tapped", removed R.O.S.A.'s batteries and replaced them with Carbon Rods, causing R.O.S.A. to undergo a critical meltdown and forcing Maggie Simpson to shove R.O.S.A. into the nearby miniature nuclear reactor alongside herself in a failed effort to stop the meltdown (in a similar manner to the ending sequence for 2001: A Space Odyssey).
- In the current (late Season 20-present) opening sequence to the show, after she pops out of the grocery bag in the cart during the Marge and Maggie supermarket scene, Maggie is shown to be turning her head around, and shaking her fist angrily at Baby Gerald, who is in the cart next to her.
- Baby Gerald's last name was seen on a label of the Simpsons.
- In his debut appearance in "Sweet Seymour Skinner's Baadasssss Song", his onesie is dark purple and his bonnet is light purple for unknown reasons. Also, his mother's arms are only shown here as well.
- His neck hair is seen in The Longest Daycare.