Answer: Many members of this family can cross and the resulting seeds can grow into so-called mutant squashoids the following year; sometimes the seeds are present in the garden via home made compost or via the previous year's crop being left on the ground over the winter. Often the first flowers are male followed by female blooms, so you might keep an eye and see what begins to develop. The only way you will able to begin to identify it is to grow it out and check the resulting fruit.
On the other hand, some of the progeny of these random crosses are basically weedy and do not have the excellent producing qualitites of their parents. If the crop is especially late for example you may not see the mature fruits before frost. If you are truly frightened by it you could tear it out now.
There is one caveat however. If you planted a so-called all female cucumber variety or one of the gynoecious cucumbers this year, this plant may have been included in the seed packet or seedlings as a pollen source for your main variety. In this case, you need to allow it to grow and bloom to assure good set on your cucumbers. I hope this helps.
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