Shermy is one of Charlie Brown's acquaintances, named after one of Schulz' friends from high school. Shermy Plepler. (See Shermy's first appearance in Charlie Brown's profile here). He started off as a main character in the series, only to be overshadowed later on by the others. He was often portrayed as being better than Charlie Brown at many things, sports in particular. He sometimes played first base on the baseball team. He appeared in several of the Charlie Brown specials, and complained about being cast as a shepherd in the Christmas play in A Charlie Brown Christmas, saying he was always cast that way. He disappeared completely from the comic strip later in years.
Below is a list of minor characters I've gathered. When I find some pictures of each, I'll add them here.
Eudora's first appearance was on June 13, 1978. She was friends with Sally Brown and had a similar crush on Linus. She played on the baseball team next to Lucy. She wore a beanie and she had straight long hair. One time, she waited with Linus in the pumpkin patch for the Great Pumpkin. She was outgoing, but very lazy.
Miss Othmar was Linus' teacher in the late 1950's. She was never seen in the strip, along with most of the adults. Linus had a huge crush on her for a long time (See Linus' character bio for more details) She eventually married, becoming Mrs. Hagemeyer, however, Linus continued to call her Miss Othmar, and other characters began calling her by that name as well. She spoke briefly to Sally in the TV special You're Not Elected, Charlie Brown.
Joe was Charlie Brown's baseball hero. He appeared in the strip a few times, but remained unseen. Joe was not a very good player. He had a very low batting average, and at one point, he was sent back to the minor leagues. Charlie Brown was very upset about this and tried to write a letter to him, but couldn't finish it. Charlie Brown is seen in strips trying to purchase Shlabotnik collectibles. He had a couple of attempts to meet and have dinner with Joe, but Joe kept getting the address and date wrong, or he'd get lost. In some 1996 strips, Charlie Brown tried to get his autograph, but it ended up being a forgery because it was spelled wrong.
Truffles first appeared on March 31, 1975. She was the first female who Linus had a crush on. However, Linus' relationship with Truffles would be short-lived twice, first by Snoopy as he and Linus went on a truffle hunt. Two years later, when Linus saw her while on a school field trip. Sally, with help from Snoopy, saw to it that his reunion with Truffles was not going to happen.
World War II, also known as "The Cat Next Door" or merely the Stupid Cat who lives next door, is Snoopy's biggest foe. He is owned by Charlie Brown's next door neighbor. Snoopy is quoted as saying about the cat, "Kitten?! That stupid 'kitten' weighs three hundred pounds!"
The cat is never seen except for its arm. Many strips show Snoopy teasing the cat from his doghouse, after which the cat slashes his house, leaving a small portion behind.
At one time, Snoopy thought that Woodstock was fighting with the cat, and he raced to help. It turned out to be a yellow glove, but this was the first time Snoopy actually stood up to the cat. Linus van Pelt went over to apologize for Snoopy's intrusion, but was promptly beaten by the cat. Peppermint Patty, when she thought that World War II was Snoopy in a cat costume, was also beaten. It was at that time that the Cat was named as World War II. I'm guessing this was due to the fact that Schulz served in WWII.
The school building where the Peanuts Gang went to school became a character when Sally Brown started talking to it in 1975, at first out of spite, but soon, it became a close friendship. It, or "he", had visible thoughts, and could drop a brick on anyone's head who gave him problems. His usual victims being Lucy and Linus van Pelt. He mostly talked about the dreary things in life, and had a bad opinion about the students and faculty. In 1976, the building collapsed, or, as Sally put it, "committed suicide". There were future school building appearances, but it was never mentioned whether or not it was the same school. I found out that later on the school was based on Jean Schulz, his second wife. I'm not really sure why.
Lila was the original owner of Snoopy, before his life began with Charlie Brown.
Lila was first mentioned in the 1960s. She had taken Snoopy home from the Daisy Hill Puppy Farm, but had to return him after her family moved to an apartment where they didn't allow dogs. She finally appeared in the strip in 1968. She was named for Lyala Bischoff, Schulz' secret crush in high school.
In 1972 she appeared in the animated film Snoopy, Come Home. She is unexpectedly reunited with Snoopy when he comes to visit her at a hospital in Nebraska after she became ill. She told him that once she recovers, she wants Snoopy to come back to her, making him choose between her and Charlie Brown. Finally, out of love, Snoopy chooses to return to her, but he becomes very sad over leaving Charlie Brown. When Snoopy arrives at Lila's new apartment, Snoopy finds out, much to his chagrin, that Lila has a pet cat. And, once again, dogs aren't permitted there. Snoopy says good-bye to Lila and returns to Charlie Brown.
She then appeared again in "Snoopy's Reunion".
Emily first appeared in 1995. She usually dances with Charlie Brown when he's feeling down. Sometimes Snoopy comes along with Charlie Brown, which usually leads to a short visit with Emily. After her first appearance, it was revealed that she was nothing more than a figment of Charlie Brown's imagination. She did appear a few more times in the strip through 1999, although it was never resolved whether she was real or not.