According to Maron himself on the WTF podcast, this episode involved three baby actors for the role of Marc's son. The first baby cast can be seen when Shay runs out of her mother's house, but after that, Maron felt that the baby, who had mixed parents, didn't look plausibly like his possible offspring, and would generate unnecessary speculation about the plot among viewers. This led to the emergency casting of two other children, who are the ones appearing in later scenes, and episode.
He seems needy.
Carol: He is. He's a baby.