Four Sheets of Random Topps Baseball Cards...Or Are They???

Below are four pictures, each containing nine totally random cards, just as if they were in 9 pocket sheets.  This isn't a precursor to the return of the Random Topps Card of the Day (starting up again in July).  But they were selected randomly. 

The questions I am posing to you the readers are these: 

• What is the significance of these seemingly random selection of cards?
• Why these cards?
• Where did I find the information to get them?

I know on a post last month, I said I was going to do this.  Let's see if anybody is paying attention. 

I will give you one hint.  One of the cards included above shouldn't be here.  It is on here because my source included it, and it turns out that it probably shouldn't have.  But alas, it's above.

The answer before the end of the day. 

Sincerely,

JayBee Anama