Penny Peterson is the love interest of Sherman from the 2014 animated film, Mr. Peabody & Sherman. She is voiced by Ariel Winter.
She is first seen going to school as Mr. Peabody drops Sherman off.
In class, Sherman explains that George Washington never cut down any trees to the class and Penny becomes enraged as she gets into a fight with Sherman at lunch and calls him a dog after she throws his sandwich and tells him to pick it up and Sherman bites her left arm as Penny tells Mr. Purdy, the school principal about the fight and Ms. Grunion, the strict head of Children's Services and school counselor warns Mr. Peabody that she will take Sherman away from his care if she deems it to be unfit.
Mr. Peabody invites Penny and her parents, Mr. and Mrs. Peterson to dinner at his house and Sherman becomes shocked that Penny came to his house as Penny sits in a chair and Mr. Peabody tells Sherman to talk to Penny, but don't tell her about Mr. Peabody's secret time machine, the WABAC.
Penny asks him how does he know all about George Washington. Sherman becomes worried about the fight again and tells her the truth, but Penny doesn't believe him and accuses him as a liar, so Sherman disobeys Mr. Peabody's rules and shows Penny the WABAC.
At first, Penny is surprised upon seeing a time machine for the first time and Sherman takes Penny on a time trip with the WABAC in order to see George Washington and entered their next stop, Ancient Egypt where Penny flees from Sherman and Sherman becomes shocked of how Mr. and Mrs. Peterson might react, so Sherman goes back to the present and asks Mr. Peabody for help as Mr. Peabody discovers that he used the WABAC, but Mr. Peabody decides to help Sherman out.
Mr. Peabody and Sherman discovered that Penny is being treated as an Egyptian princess resembling Cleopatra as Mr. Peabody convinces Penny to come home, but Penny tells the two that she is already engaged to King Tut, but Mr. Peabody informs her that King Tut dies young and Penny refuses to to believe him.
However, Mr. Peabody also tells her that after King Tut's death, she will be mummified a.k.a. killed.
After Penny decides that she wants to go back with Mr. Peabody and Sherman, she gets taken away to the wedding as Mr. Peabody and Sherman are imprisoned, the two manage to escape and impersonate Anubis, the God of Death to rescue Penny as Penny is happy to see Sherman again.
The three quickly flee to the WABAC and leave ancient Egypt. The three enter the renaissance-era Italy where they meet Leonardo Da Vinci an artist and the inventor of the helicopter and other flying machines.
As Penny and Sherman go to Da Vinci's workshop and discover his old prototype flying machine, the two take it out for a spin and they enter Florence as they crash into the water after Mr. Peabody has caught them fooling around with one of Da Vinci's inventions.
Mr. Peabody scolds Sherman for destroying one of Da Vinci's inventions while returning home but Penny tells him that Sherman will be taken away if Ms. Grunion finds out. The three then enter the Trojan attack on Troy as Mr. Peabody calls Sherman a bad boy as the WABAC crashes on the Trojan attack on Troy.
Sherman joins the Trojan army as Shermanus and Mr. Peabody and Penny search for him. They find themselves in the battle, but Penny becomes trapped in the Trojan horse.
In a rescue attempt, Sherman and Penny are saved, but Mr. Peabody is presumed dead. Sherman and Penny must rescue Peabody as they return to the present minutes before Sherman tells Mr. Peabody for help.
However, the present copies of Mr. Peabody and Sherman show up along with Ms. Grunion. Ms. Grunion manages to reclaim both Shermans, but all of the copies of Sherman and Mr. Peabody merge and disrupt the space-time continuum.
Peabody, Sherman and Penny flee to the WABAC, but they can't travel back in time as several famous historical figures and monuments fall down to the present.
Mr. Peabody tells everyone the truth and also tells that he would rather be a dog than a father and an inventor as the three presidents reward Peabody a presidential parodon.
As the vortex in the space-time continuum rips open, Sherman pilots the WABAC to travel to the future and reverse everything as all of the historical figures and monuments return to their timeline and drags Grunion with him as she gets revenge on Peabody someday if she returns.
Peabody and Sherman return spotaneously as the Petersons look on and begin a celebration as Penny begins to have romantic feelings for Sherman and the two began a romantic relationship as they become a couple.
Towards the end of the film, she and Sherman head back to school for a fresh start as everything is back to normal.