|Other languages:|| German: Mauseherz|
|Notables:|| Martin Burgess|
|TV Show:|| "Of Mouse and Man"|
"Last Grimm Standing"
"Cat and Mouse"
"The Bottle Imp"
"To Protect and Serve Man"
"Natural Born Wesen"
"One Angry Fuchsbau"
"The Wild Hunt"
"My Fair Wesen"
|Books:||The Killing Time|
Martin Burgess was killing people in his neighborhood who challenged him due to an abusive life with his father. His victims would challenge him and become aggressive, and Martin's mind would turn them into his father. When cornered in his junkyard, he looked into a mirror and, horrified, saw himself as his father, allowing the police to arrest him.
Sauly was a bookie who had many connections and sold tickets to various shady, underground events such as the Löwen Games. Monroe went to him for tickets to the Löwen Games, and threatened him with his Blutbad form. Sauly then gave him an address where someone would pick him up and take him to the games, when in reality Sauly set Monroe up to be taken in to fight.
Reginald was the owner of a camera store and made fake papers for members of the Resistance to get out of the country. He was first visited and threatened by Edgar Waltz for the location of Ian Harmon. Waltz threatened to kill his family if he didn't comply. Rosalee also came in to get fake papers for Ian. Reginald gave her the passport and money, along with a note saying "I'm sorry. I had no choice". He was later killed by Waltz.
Leroy Estes comes into the shop for an order that he made with Rosalee. He's extremely unbalanced and wobbly due to an unknown inner ear affliction. Monroe accidentally mixes in the wrong ingredient and, due to his mistake, the mixture that would have been Leroy's antidote instead made him act manically, cutting up furniture with a chainsaw. He is later knocked out by Monroe in his home, where Monroe proceeds to give him the correct serum.
Leroy, the same Mauzhertz from "The Bottle Imp", is seen among the crowd of other Wesen in Rosalee's shop, demanding that Rosalee take action about the Gesetzbuch Ehrenkodex being broken. He and the rest of the crowd later leave, slightly disappointed about Monroe and Rosalee's responses.
Katherine Nidaria is seen scared of Don Nidaria, her husband, in a flashback that occurred six months ago. Don is angry at her for wearing the wrong dress, and in a rage, Don throws Katherine off their balcony, killing her.
Leroy Estes goes to the spice shop to buy something that he has to steep for 15 minutes before and after every meal for a week.
When Trubel is trying to help Nick and Hank with their case, she runs up to Megan and pins her against some wood causing her to woge into a Mauzhertz. She pleads for her life and Trubel demands to know what Cammy has been up to. Megan gives in and tells Trubel that Cammy met Donna O'Hara at O'Bryant Square. Nick and Hank arrive and pull Trubel away from Megan, and Trubel tells them what Megan said.
When they woge, they gain beady eyes, whiskers jutting out from a pointed nose, more facial hair, large ears and oversized incisors. Female Mauzhertz have an overall similar woge, but their amount of facial hair varies from none at all to almost as hairy as males, and they have less pronounced whiskers. They do not have any strength enhancement and are generally quite weak.
Mauzhertz are, by nature, very timid and exceedingly cowardly, oftentimes afraid of their own shadow. They are very predictable which makes them easy prey for Lausenschlange, their natural predators.
Mauzhertz are a friendly species, and will go out of their way to avoid trouble. Consequently Mauzhertz have never been at odds with the Grimms. Prior to Nick Burkhardt recording Martin Burgess' murder spree, it is unlikely that a Grimm had ever recorded an instance of a rogue Mauzhertz, as Nick could find no mention of them in any of his Grimm Diaries, and required Monroe's help to identify them.
Despite their passive natures, Mauzhertz can occasionally be found in the seedy parts of society. A good example of this would be Sauly, who had connections and sold tickets for Leo Taymor's Löwen Games. Likewise, Nick spotted at least one Mauzhertz in prison. ("To Protect and Serve Man")