After the death of his father, Marius, age 7 at the time, inherited a cravat and an epaulet factory, quickly gaining prominence among the richest of the rich in his home area.
In "Northwest Mansion Mystery," Mabel Pines, Candy Chiu, and Grenda discover and fall in love with him while looking at the guest list for Northwest Fest, but, fearing he may be out of their league, hesitantly make a pact not to pursue him. However, Mabel and Candy go back on this promise and attempt to use their "combined cuteness" to have a shot with him, excluding Grenda and her "aggressive" flirting style; they have no success. When Grenda learns what her friends have done, she approaches him and flirts as she always does, and Marius ends up falling for her.
In "Dipper and Mabel vs. the Future," Grenda mentions going to Austria to visit his castle at the end of the summer.
In the end credits of "Weirdmageddon 3: Take Back The Falls," Grenda and Candy visit him during the final days of summer. They are shown travelling in his yacht with Grenda giving him a big kiss.
Marius is roughly the same height as Grenda. He has fair skin, thick eyebrows, a large, pointed chin with a cleft, and shoulder-length brown hair. Much like Grenda, he has a red mole on his left cheek. Marius wears a white shirt with a long cravat under a red military tunic with gold epaulets, white pants and gloves, and black riding boots. He also wears a military medal with a green and white ribbon on his chest.
- 210. "Northwest Mansion Mystery"
- 217. "Dipper and Mabel vs. the Future" (mentioned)
- 220. "Weirdmageddon 3: Take Back The Falls" (no lines)
"Wait! Don't go! Grenda, was it? I must speak with you. There's something about you, I can't get you out of my head. You're so bold and confident! I know you're probably out of my league, but, might I give you mein phone number?"
"After inheriting his father’s cravat and epaulets factory at the age of 7, Marius Marius von Fundshauser quickly rose to prominence as the richest rich boy in Richardson Richington’s Rich Boys Richcademy, Furtherrich, he richly riched rich rich rich rich rich, rich rich rich. Rich."
- His phone number is 555-0516.
- In a possible reference to Marius, Dipper's and Mabel's Guide to Mystery and Nonstop Fun! predicts that Grenda will marry someone rich.
- A baron is one of the lowest ranks of nobility, just below count. The German word for baron is Freiherr (literally "free man"). German noble titles go between first and last names, so Marius' full name in German would be Marius Freiherr von Fundshauser.
- If real life facts are taken into account, he would only be known as Marius von Fundshauser outside of Austria, as nobility titles have been abolished there since 1919. However, in Germany they do still exist.
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