Bowser Memory P
From the Super Mario Wiki
Bowser Memory P is a character found in Mario & Luigi: Bowser's Inside Story. When Mario and Luigi first entered Bowser's Memory Banks they encountered a round, Napse-like being tending to the computer-like interface of Bowser's mind. It then scanned them and Starlow and determined that they were "viruses", transforming into digital dopplegangers of the Mario Bros. known as Bowser Memory ML, and attacking. After being defeated, it switches to an observation protocol and to 'aid communication" between it and Mario, Luigi and Starlow, where it briefly transforms into its Bowser Memory P form, which resembled Princess Peach. The Memory P reveals that when Bowser was rammed by the Fawful Express, it joggled some memories around. It then changes back to its original spherical form and goes through the library-like books of memory, pulling out both a memory of steak and Peach before finding the broken memory of the safe combination for the Mario Bros.
In order to put the memory back together, Mario, Luigi and Starlow must piece it back like a puzzle. The end result is the safe number (9898-88241-983), which it puts back into Bowser's memory bank. Instantly, Bowser remembers the combination, and hums the song he used to remember it as he opens the safe. Inside the safe is where he obtains the second Star Cure, before being subsequently trapped in the safe by the Elite Trio.