In Mega Man 4, the support robot that gives Mega Man random items at designated points is Eddie.
Eddie, also known as Flip Top, was introduced in Mega Man 4 as one of Dr. Light’s support robots. Rather than functioning like Rush, who provides selectable traversal abilities, Eddie appears at specific locations during certain stages and offers Mega Man a randomly selected item.
The possible rewards can include health, weapon ammunition, or an E-Tank. Because the outcome is random, Eddie can feel like a small lottery: he may provide exactly what the player needs or deliver a less useful resource. That uncertainty is the defining feature of his role in this game.
The other choices belong to different parts of Mega Man’s support-robot history. Rush is Mega Man’s dog-like companion and gains Coil, Jet, and Marine forms in this installment. Beat is associated with later support mechanics, while Tango is a cat introduced in Mega Man V. Eddie continued appearing in later games, but Mega Man 4 established his item-dispensing gimmick.