Professor McGonagall from the Harry Potter series is an ISTJ (request)
ISTJs are quiet and reserved individuals who are interested in security and peaceful living. They have a strongly-felt internal sense of duty, which lends them a serious air and the motivation to follow through on tasks. Organized and methodical in their approach, they can generally succeed at any task which they undertake.
ISTJs are very loyal, faithful, and dependable. They place great importance on honesty and integrity. They are “good citizens” who can be depended on to do the right thing for their families and communities. While they generally take things very seriously, they also usually have an offbeat sense of humor and can be a lot of fun - especially at family or work-related gatherings.
ISTJs tend to believe in laws and traditions, and expect the same from others. They’re not comfortable with breaking laws or going against the rules. If they are able to see a good reason for stepping outside of the established mode of doing things, the ISTJ will support that effort. However, ISTJs more often tend to believe that things should be done according to procedures and plans. If an ISTJ has not developed their Intuitive side sufficiently, they may become overly obsessed with structure, and insist on doing everything “by the book”.
The ISTJ is extremely dependable on following through with things which he or she has promised. For this reason, they sometimes get more and more work piled on them. Because the ISTJ has such a strong sense of duty, they may have a difficult time saying “no” when they are given more work than they can reasonably handle. For this reason, the ISTJ often works long hours, and may be unwittingly taken advantage of.
The ISTJ will work for long periods of time and put tremendous amounts of energy into doing any task which they see as important to fulfilling a goal. However, they will resist putting energy into things which don’t make sense to them, or for which they can’t see a practical application. They prefer to work alone, but work well in teams when the situation demands it. They like to be accountable for their actions, and enjoy being in positions of authority. The ISTJ has little use for theory or abstract thinking, unless the practical application is clear.
ISTJs have tremendous respect for facts. They hold a tremendous store of facts within themselves, which they have gathered through their Sensing preference. They may have difficulty understanding a theory or idea which is different from their own perspective. However, if they are shown the importance or relevance of the idea to someone who they respect or care about, the idea becomes a fact, which the ISTJ will internalize and support. Once the ISTJ supports a cause or idea, he or she will stop at no lengths to ensure that they are doing their duty of giving support where support is needed.
The ISTJ is not naturally in tune with their own feelings and the feelings of others. They may have difficulty picking up on emotional needs immediately, as they are presented. Being perfectionists themselves, they have a tendency to take other people’s efforts for granted, like they take their own efforts for granted. They need to remember to pat people on the back once in a while.
ISTJs are likely to be uncomfortable expressing affection and emotion to others. However, their strong sense of duty and the ability to see what needs to be done in any situation usually allows them to overcome their natural reservations, and they are usually quite supporting and caring individuals with the people that they love. Once the ISTJ realizes the emotional needs of those who are close to them, they put forth effort to meet those needs.