Since I'm not acquainted with this 'mr don't tell anyone comic story', I cannot determine the main characters. It would be great if you could find someone who has read it or look for official summaries that might mention the key characters.
Obviously, the main characters are Mr Black and Mr White.
As I don't know the story, I can't say for sure. But perhaps Mr Brown is kind - hearted and Mr Black is a bit more strict.
Since I don't know the exact Mr Hippo story, but likely Mr Hippo himself is a main character. There could also be other animals like birds, monkeys or zebras depending on the setting of the story. If it's a story about Mr Hippo's family, then there might be Mrs Hippo and little Hippo calves as main characters too.
Since we don't know the exact Mr Whiskers game, Mr Whiskers himself is likely to be one of the main characters. If it's a game with a lot of interaction, there might be a sidekick character, like a little bird that gives Mr Whiskers hints or helps him fly over difficult areas.
In the 'Mr Wright Christmas Story', Mr Wright is likely the central character. There could be other characters such as his neighbors. If it's a story about Christmas in a community, the neighbors might play important roles, like helping Mr Wright with Christmas preparations or joining him for a Christmas party. There could also be characters like Santa Claus if it has a more traditional Christmas element in it.
Mr Bean is the central figure in 'Mr Bean Love Story'. He is the one whose actions drive the story forward. The other important character is the woman he has feelings for. She might be an ordinary woman who just happens to cross paths with Mr Bean. Mr Bean, with his unique personality, then tries to win her over in his own clumsy way.
The Mr Gingerbread Man is the star of the story. He's made by an old woman and an old man, so they are important characters too. In some tellings, animals like cows, horses and pigs also interact with the gingerbread man during his run. But the most notable among the other characters is the fox. The fox is cunning and tricks the gingerbread man, which makes it a key character in the story.
I assume Mr Nibbles is one of the main characters, as he is in the title.
Since I don't know the exact 'Real Mr Goodbar Story', I can't say for sure who the main characters are. But I assume Mr Goodbar himself would be one of the main characters. There might also be friends, family members or foes depending on the nature of the story.
Well, in the Mr Men Christmas Story, Mr Greedy could also be a main character. He might be eyeing all the delicious Christmas treats. Little Miss Chatterbox would be chatting away about all the exciting Christmas plans. There are also other characters like Mr Strong who could be helping with lifting heavy Christmas decorations or building things for the celebration.