How do I remove a stuck Mini CD from the SuperDrive on a Macbook Pro?
Do not stick anything else in the slot. Really.

The inject / eject mechanism is keyed for a full sized disc and you don't want to wedge it in the wrong direction or retract that delicate part any further by fishing around inside the narrow slot. There is no eject button so you will need either luck or finesse and skill to get the CD out.

Power down the Mac and hold it firmly with the Apple logo facing you at chest height with the CD slot pointing to your lap. Gently rock and shake it to see if the CD is loose and encourage it to peek out the felt skirt that is inside the unibody enclosure.

Your Mac when powered off is very strong and you gently start it down and then quite forcefully yank it back up vertically. One or two shakes is all it takes to get the mini CD poking out just a bit. At that point, the felt will hold it and you can return the Mac to a level table and use tweezers or needle nose pliers or nimble fingers to remove the CD.

If you can't get it out - take it in for service. Unless you work on these regularly, you don't know which model superdrive is in your Mac and how hard, deep, gentle you can be with tools to help dislodge the CD. Also, if you are comfortable popping the back off your Mac - you could use iFixit to get to the drive itself and the CD will likely fall out once you have that component out of the Mac and away from the felt skirt.

Again, have a good firm grip - if you are so nervous that your palms are sweaty, that's your signal to see about getting a technician to help or waiting a bit to convince yourself you can shake it loose. These computers are made to endure UPS and FedEx shipping, packing in luggage in a bumpy car and your shaking should be on that level of violence and no more. If it's lodged behind the eject mechanism, you'll need someone to get inside and clear things in most cases.