Hello. There is an easy way around this. Stay with me as this sounds made up, but I swear it works.
1. Go to Test Your Luck from the main menu.
2. Select your character, and select expert.
3. Let the slots start spinning on their own (ignore the begin button, its just easier IMO).
4. Immediately after your opponent is selected, hit the X Button (xbox360) 7 times relatively fast.
5. It should land on the MK Symbol. When it does, immediately hit the Y Button (xbox360) 7 times relatively fast.
6. Again, it should land on the MK Symbol. When it does, immediately hit the B Button (xbox360) 7 times relatively fast.
NOTE: The MK symbols have to be available in all slots. If not, just keep retrying until they are. This is by far the most annoying part. I tried this strategy after getting tipped off to it and it worked on my first try when the MK symbol was available in all 3 slots. Also, I have no idea if it works on the PS3, but logic says it does, obviously with its respective buttons. Be patient.