This is the much maligned (by nursery growers) "Mother of Thousands" (or millions!). Though it's looked upon by growers and many others as a weed (and it is indeed an invasive weed in areas where it can winter over), it's nevertheless a source of fascination and admiration for many. When they flower, the mother plant dies, but not before it has produced enough babies to populate every pot in the greenhouse. A one-plant population explosion. And it's reported to be very toxic to children and small pets if ingested.
We might as well like it, since we'll never eliminate it's presence in the greenhouse.