Aaron Denlinger recently wrote a post at Reformation 21 describing his daughter’s recent interest in baptism after seeing a baptism in church. He referred to some stories from church history related by Marcia Colish in her recent Faith, Force and Fiction in Medieval Baptism Debates:
In the early church stories arose of pagan persons who pretended baptism as part of Roman plays enacted on stage in mockery of Christian beliefs. In other words, water was applied to individuals in the Triune name not in the interest of actually conferring the sacrament, but in ridicule of Christian faith and ritual. But, according to Christian legend, the actors undergoing baptism in mockery of Christian practice were on more than one occasion actually converted by the sacrament, and then immediately announced as much to their fellow-actors and audiences, and — without fail — were martyred either by the unimpressed crowds or civil authorities who happened to be in attendance. This apparently happened to one Ardalion in 293, one Gelasinus in 296, and one Porphyrius in 362.
Roman actors weren’t the only ones engaging in pretended baptisms. The fourth-century historian Rufinus tells a story of the Alexandrian Bishop Alexander observing several young boys mimicking Christian baptism on the banks of the river Nile. Intrigued (and somewhat troubled) by the scene, Alexander had the boys brought to him and interrogated them regarding their play. When one boy among them who had assumed the role of “bishop” described to Alexander the words and rite he had employed in baptizing his friends, Alexander concluded that the baptisms administered were in fact valid, and that the baptized boys should subsequently be catechized. The young baptizer (who himself came under care of the church) was no other than Athanasius, the future (real) bishop of Alexandria who championed the cause of Nicene orthodoxy for much of the fourth century.
The stories of actors and children pretending — whether innocently or not — baptisms which, by one judgment or another, proved valid if not effective, figured significantly into later patristic and medieval conversations about the proper criteria for baptismal validity and efficacy. So Augustine, for example, reckoned that pretended baptisms were genuine and that recipients of such, even if genuine faith came later, should not be re-baptized, but denied that such baptisms were ultimately effective (as instruments for those spiritual realities which baptism signifies, such as the remission of sins) until the persons so baptized came to genuine faith and repentance (See Augustine’s On baptism 1.12). This of course complemented Augustine’s position on baptisms administered by profane or heretical persons — such baptisms, according to Augustine, were likewise valid (but ineffectual unless or until the baptized joined himself to the true church). Thomas Aquinas took a slightly stricter view on these matters, arguing that proper intent to receive baptism was a criterion for baptism’s validity (at least for those of sufficient age to intend), thereby raising doubts about the authenticity (and so, by implication, the purported efficacy) of at least those baptisms received by Roman actors.