These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
And it doesn't help that at Parappa 2's final stage, PaRappa is singing to Lammy, who's playing with him on stage, while Sunny is just watching from the audience with her father.
Teriyaki Yoko. Especially when you fail and she rises out of the ground, 100 times her size. Even in the American version.
Also when you get the song wrong with octopus hairdresser he makes a frightfully angry that scared a few players.
Scrappy Level: The fifth level in the original (thanks to a sudden Difficulty Spike in having to out-rap every previous Master) and the sixth level in Lammy (while not as difficult to play by itself, some people find the background music for the level to be simply god-awful).
That One Boss: Potentially, any of the bosses, but Cheap Cheap the Cooking Chicken is consistently hard for a lot of people.
That One Level: The bathroom rap level is considered to be extremely frustrating due to how many buttons the player has to play back with near perfect timing in order to succeed. This was probably one of the reasons why the sequel has a more forgiving mechanic for button pressing in the levels.
Um Jammer Lammy-only examples:
That One Level: Many players have the toughest time with Cathy Piller or Teriyaki Yoko. The former gets lampshaded in the game.
