Upon killing Pac-Man in the Secret Cow Level, a red portal will open up leading to the Secret Pac-Man Level.
This level replicates the original Pac-Man game.
To eat the dots, the character must transform into Pac-Man. This can only be done using a charge of the Cherry dropped by Pac-Man.
The ghosts (Blinky,Clyde, Inky, Pinky) are only vulnerable if a Power Pellet is eaten. Otherwise, they are invincible.
For some reason, sometimes, when as Pac-Man, you cannot eat the dots and/or power pellets. You will have to find Pac-Man again in the Secret Cow Level and hope it doesn't bug out again.