Bootler

Bootler is a Boo butler who works for Lady Bow in Boo's Mansion. He also acts as her personal advisor. Bootler is very protective of Lady Bow, and initially does not want her to join Mario on his quest to defeat Tubba Blubba (and even then wishes to go along with her, though she does not allow him to do so).

Bootler seems to have a certain connection with Lady Bow's ancestors. He constantly reminds her that the ancestors would be displeased if she was harmed in any way. According to a seemingly knowledgeable Toad found near Toad Town's port, Bootler was once in love with Lady Bow's grandmother, who was apparently Boo's Mansion's mistress during Bow's early childhood. This Toad also reveals that, in his youth, Bootler traveled the globe with Goompa and Koopa Koot.

After Mario defeats the Shadow Queen in Paper Mario: The Thousand-Year Door, Lady Bow and Bootler go to Poshley Heights for a nice (but expensive) vacation.

Bootler has legendary status as a master frightener. He even scares Fice T. and Mario (and possibly the player too) at the entrance of Forever Forest. Bootler seems to enjoy scaring Fice T., as implied in the letter he sent to him.

Trivia

 * "Bootler" is word play off of "Boo" and "butler". Goombario actually states that "the correct term is 'butler'" upon tattling Bootler, indicating that the portmanteau in his name may have simply been caused by the unique Boo speech patterns seen exclusively in Paper Mario (which do indeed involve replacing words and parts of words with "Boo").
 * Bootler is the only known Boo to have facial hair, save for the seemingly living Boo portraits (such as Boo's Portrait) found lining Boo's Mansion's second floor and Mario's Boo Mario form.
 * A Bootler poster appears in Super Paper Mario as a collection of Francis.
 * Bootler is the only minor character in the Paper Mario series to make a visual appearance in all three games, aside from Whacka, who is likely three different Whackas in all his appearances.