Hi Cassie! 

Your plant has a hitch hiker! The black spots do appear to be frass (a fancy name for poop) from the caterpillar feeding on the plant. 

Caterpillars in houseplants is not a usual occurrence. I found little information in my research. I would assume that a moth or butterfly made a stop at this plant and laid its eggs. Or the eggs were present in the soil or potting media that was used to pot up your plant. You may find additional caterpillars on the plant if there are eggs unhatched in the potting media. You may want to shake the plant over a sheet of white paper to dislodge any additional caterpillars. 

Something that may help for caterpillar control is a product called Bt (Bacillus thuringiensis) Here is information from a bulletin put out by MSU Extension:

Bacillus thuringiensis (B.t.)

Products containing B.t. are made from a naturally-occurring soil bacterium. Many different B.t. products are available for landscape professionals and homeowners. Different strains of B.t. target specific pest groups, making them selective pesticides. For example, spores and crystals of Bacillus thuringiensis var. kurstaki (B.t.k.) are highly toxic when ingested by butterfly and moth larvae (caterpillars). The crystals containing the toxin dissolve only at an extremely high pH found in the caterpillar’s gut. B.t.k. is not toxic to bees. However, avoid spraying or allowing spray to drift onto favored food plants of caterpillars such as milkweed, the sole food source for monarch butterfly caterpillars.

 You would spray the foliage top and bottom. If any caterpillars feed on the foliage they will perish.  

Another option would be to re pot the plant in fresh potting media. I would remove all the existing potting media, shake way as much as you can from the roots and rinse the entire plant with water. Dispose of the potting media you removed in a seal plastic bag and put out in the trash. Carefully repot the plant. 

Here is a fact sheet on repotting house plants from Penn States Extension: https://extension.psu.edu/repotting-houseplants

I hope you find this information helpful!