I have two questions:

1. Is there a way to turn a white cake mix into a chocolate cake? I normally make the WASC cake and don't have a chocolate cake mix and don't want to drag my kids to the store to buy one, so could I just add some cocoa powder or melted unsweetened chocolate or chocolate chips? And how much would I need?

2. I only have medium eggs. Do I need to add extra eggs to make up for them not being large?

Thanks!

..moving to Recipe Tips & Ideas.

I think I remember reading somewhere that you can add an extra egg without issue, I personally would use 4 if they're medium (I usually use extra-large)...
About the chocolate cake - I would add some cocoa powder, maybe use chocolate milk for your liquid? That would probably work...I wouldn't wanna drag the kids out either if I didn't have to!