Sometime we stop too soon. Today's Rashi is a case in point.
On Exodus 8:6 Rashi cites an amusing story that is also strong evidence of God's sense of humor. We are told that He, in his wisdom, sent a single frog to afflict the Egyptians. Whenever an Egyptian struck the frog in fear, anger or frustration, the frog broke apart into streams and streams of frogs that soon covered the land.
The story of the Magic Multiplying Frog is in the midrash tanchumah, and you can't swing a cat by its tail on a playground in Boro Park without hitting a little kid who knows it, believes it, and would probably fight you if you raised an eyebrow at it. Unfortunately, the story, likely, has no basis in fact, as Rashi himself suggests in the little-read, much-ignored second half of his comment to Exodus 8:6.
One frog is a "tzefarday-ah." Many frogs are "tzefardah-im." In Exodus 8:6 we're told that the "tzefarday-ah" (ie: one frog) covered the land. The story of the Magic Multiplying Frog explains this anomaly, says Rashi in the first part of his comment.
In the second part of the comment, Rashi says (I'm paraphrasing) "You know what? Maybe the use of the singular isn't so strange. After all, the singular is used to identify the swarm of lice (keenom, not keenim) that overtook Egypt in the very next plague, and the singular is used for the fish (daga, not dagim) who die in the river during the plague of blood. So perhaps the singular in our verse simply refers to one swarm of frogs, Rashi concludes.
So here we have two possible explanations, one involving grammar, the other involving magic. Which, oh which, will the masses embrace? Think. Think.