Ultimateboy13 and his Friends' meets Mrs. Doubtfire

Ultimateboy13 and his Friends' Adventures in Mrs. Doubtfire is the first in the s series Ultimateboy13 and his Friends' Adventures made by Ultimateboy13.

Plot
Daniel Hillard is a voice actor living in San Francisco, California. Though a devoted, loving, and well-meaning father to his three children, Lydia, Chris and Natalie, Daniel is a poor disciplinarian and his wife, Miranda, considers him unreliable. One day, he quits his job at an animation studio over dispute over a questionable script. After he left the studio, he meets Ultimateboy13 and his movie character friends and brings them to his home to throw a chaotic birthday party for Chris, despite Miranda saying that Chris could not have one because of his bad report card. Returning home from work due to a neighbor's complaint, she meets Ultimateboy13 and his movie character friends. Miranda is furious with Daniel for having planned and thrown the party behind her back, and, after a heated argument, reaches the end of her patience and files a divorce. The gang felt very sorry for the divorce, at their first custody hearing, the judge initially grants Miranda sole custody of the children, since Daniel has neither a residence nor a job, but tells Daniel that he will order joint custody if the former gets a suitable residence and job within 3 months.

As Daniel works to rebuild his life, getting a menial job at a TV station, he learns that Miranda intends to hire a housekeeper and surreptitiously alters her classifieds form when she refuses to let him take care of the children. He then calls Miranda several times, using his voice acting to trick her into thinking that bed job applicants are calling, Ultimateboy13 gives Daniel an idea to pretend to be "Mrs. Euphegenia Doubtfire" who lives in the land where Ultimateboy13 and his movie character friends live. Daniel agrees and then calls Miranda, imitating Mrs. Euphegenia Doubtfire's voice. Impressed with her alleged qualifications, Miranda invites "Mrs. Doubtfire" for an interview. Daniel enlists his brother Frank, a makeup artist, and his partner Jack to transform him into the character.

After being further impressed by the interview, Miranda hires Mrs. Doubtfire. The children initially struggle to adjust to Mrs. Doubtfire's strict methods, but they soon begin to thrive, becoming happier and doing better in school, while Miranda is able to heal her strained relationship with them as she and Mrs. Doubtfire become good friends. Daniel has to learn several skills to play the role convincingly, such as cooking and cleaning, and also improves himself. However, despite impressing Miranda greatly with his newfound maturity, Daniel soon realizes that he has indirectly created another barrier, as when he asks to look after the children, Miranda insists she could never dismiss Mrs. Doubtfire, as the family's lives have been made so much better by "her." One night, Chris and Lydia accidentally learn that Mrs. Doubtfire is their father in disguise, but after the initial panic and learning why he did it, agree to keep it a secret and are happy to have him back in their lives.

One day, Jonathan Lundy, the CEO of the TV station Daniel works at, sees Daniel clowning around with toy dinosaurs on the set of an unsuccessful children's program on the cusp of cancellation. Impressed with his creativity, Lundy invites him to dinner at Bridge's Restaurant on the coming Friday night in order for Daniel to pitch ideas as a possible new host. Miranda, meanwhile, expects Mrs. Doubtfire to attend a birthday dinner arranged by her new romantic interest Stuart Dunmire scheduled at the same time and place.

Unable to reschedule his dinner with Lundy and not wanting to disappoint his family, Daniel goes to the restaurant and tries to rotate between both dinners, changing in and out of the Mrs. Doubtfire costume in the restroom. He consumes several alcoholic beverages between the two tables and becomes tipsy. He forgets to change out of the Mrs. Doubtfire costume before returning to Lundy's table and seasons pepper, an ingredient Stuart is allergic to, on Stuart's order. When Lundy questions the costume, Daniel quickly covers for his mistake by explaining that his alter ego is his idea for a television persona, impressing Lundy. At Miranda's table, Stuart starts choking on the pepper. Out of regret, Daniel, still in the Mrs. Doubtfire costume, administers the Heimlich maneuver and manages to save him. Unfortunately, during the struggle, Daniel's mask rips off, revealing his identity. Horrified and furious, Miranda storms out of the restaurant with the children.

At their next custody hearing, Daniel demonstrates he has a job and a suitable home, then explains his action. Unfortunately, the judge, although sympathetic, is disturbed by his behavior and grants Miranda full custody, with Daniel limited to supervised visitation once a week. The ruling devastates Daniel and, unbeknownst to him, Miranda, as she realizes that he never meant any harm.

Without Mrs. Doubtfire, Miranda and the children become depressed, realizing how much "she," therefore Daniel, improved their lives. However, they are delighted when they see Daniel dressed as Mrs. Doubtfire hosting his own television program, "Euphegenia's House", which becomes a hit across several American cities. One day, Miranda pays a visit to Daniel after he wraps up one episode and, congratulating him on his success, admits that things were better when he was involved, so she forgives him, successfully appeals the custody ruling, allowing them joint custody, and makes peace with him. Later, the kids are greeted by Daniel, revealed as their new babysitter, undisguised and without supervision. They head out as Miranda watches a Euphegenia's House episode where Mrs. Doubtfire answers a letter from a little girl whose parents are divorcing, saying that no matter what arrangements families have, love will prevail.