The common noun here is "frog" as the only other noun, Many, is not a common noun - it's a proper noun.
"frog" here is the object of the sentence: it's the object of the verb "caught" of which the subject is Mary
So, Dr. Faustus is an embodiment of curiosity gone wild. His blase attitude towards humanistic science is, however, some kind of a scientific decadence: he casts away philosophy and law, to embrace magic, as a relic of medieval obsession over mysticism. In this regard, he is a subversion of the Renaissance Man. He thinks he has already learned all there was to learn about this world, so now he yearns for another kind of knowledge - esoteric, otherworldly, knowledge that isn't exactly a knowledge because you don't have to study long and hard for it, you just have to sell your soul to Lucifer.
Prepare what you are going to say! If you just say something without thinking first, it can escalate the situation even more. Hope this was helpful ;)
Get well soon, since your mental versus abilities arent that wel