Marcellus first appears in Livy's history when his father, then curule aedile, brought an action before the senate against his colleague Scantinius Capitolinus who had made improper advances to the young and beautiful boy.
The younger Marcellus, despite his evident embarrassment, convinced the senate of the man's guilt and his father was recompensed with some articles of silver which he dedicated to a temple.
The relation of this case to the Lex Scantinia is vexed, since a Roman law was named after its proposer, and never a defendant.
Marcellus himself was badly wounded; his father's body was subsequently returned by Hannibal to the son.
In 204 BC Marcellus was a tribune of the plebs, appointed to lead a commission (also including Cato) to investigate charges made against Scipio Africanus.