Gerald Samson

Gerald Samson (better known as "Baby Gerald" or "The Unibrow Baby") is Maggie's arch-nemesis.

Biography
Lisa has referred to Baby Gerald as Maggie’s rival. Gerald is distinguished by his unibrow, being one of the few characters on the show to have eyebrows. On a few occasions, Gerald has been shown being pushed in a stroller by his mother outside the Simpsons’ house, with the two babies glaring at each other, the camera focusing on their narrowed stares. He often wields a mallet. He is the first baby to show any interest in Maggie, either positively or negatively, as other babies have nothing to do with her, which is why she is always seen playing alone or with her siblings. He does not need a pacifier and can walk better than she can as she usually falls down after a few steps and crawls. Like Maggie, however, he does not speak.

Gerald's antipathy towards Maggie may stem from an unfortunate circumstance on the day they were both born in the same hospital and the last diaper was given to wrap Maggie. Gerald was wrapped in a piece of newspaper, which left him with a skin rash from which he is still suffering. Gerald 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". Maggie and Gerald battled on opposite sides of the infamous Springfield St. Patrick's Day riot, sparked by the town's ban on alcohol after Bart is spotted under the influence.

When Marge started a daycare center, Gerald was one of the babies for whom she was caring. During the day, Gerald blamed Maggie for everything he had done, including spilling Maggie's milk and breaking a lamp. As Marge was rebuking Maggie, Gerald offered to help with cleaning the mess and got a special reward. All this led Maggie to run away from home.

The Longest Daycare
At the Ayn Rand School for Tots, both Gerald and Maggie were incorrectly deemed to be of only average intelligence through a standardized brain exam and wound up in the same depressing and unattended borstal, away from the privileged rooms set aside for the high-achieving babies. Gerald smashed several butterflies with his mallet and drew squares around them as though they were paintings. He followed Maggie, who rescued a pubescent chrysalis, to retrieve it and smash it. She crawled away and managed to keep him at bay until her mother showed up to take her home. Gerald, who thought he had smashed it with the window blinds, returned to the window and saw that Maggie had outsmarted him, having left her blue bow which he dropped the window shade on, not the chrysalis, which she had hidden in one of her hands. On the car ride home with her mother, she tossed it out of the car window, watching with awe as it transformed into a beautiful blue butterfly.

Future
At some point he and his childhood nemesis Maggie fall in love and eventually marry. It is not known if the marriage lasts as she finds his constant interruptions annoying. She gives birth to a daughter (Maggie Jr.) who, as a toddler, looks exactly the same as Maggie does now, but it is unclear who the father is.

Trivia

 * In the new The Simpsons opening sequence, when Marge goes to the supermarket, it shows both Gerald and Maggie shaking their fists at each other.
 * Baby Gerald's surname (Samson) was seen in a label of the Simpsons.