Its a syno of some type. Does it swim upside down? Since it came from waltmart id assume its a Synodontis Nigriventris. I could be wrong tho. Ask this question in the Other Catfish Section. Or a friendly mod might move it..... Hope that helps
Ok it might not be a Synodontis Nigriventris. Ill try and find some others and post the website up here for you to have a more of a look in trying to figure out what Syno he is.
it is a juvenile Synodontis, very hard to tell when they are so small, which species it could be, it will more than likely grow to be grey in colour, with black dots. Anything from small to large dots. Once it has grown a bit we should eb able to ID it better.
They can become very agressive fish later in life, and normally grow up 12" or a little less.