Mr. Umlaut is a super-rich pet dentist and the owner of a Danish modern home that he turns over to Francine to sell on the show Langley Dollar Listings in the episode of the same name.
The home is made entirely of ancient Danish Alderwood and must be kept at precisely 64.2% humidity at all times, And even includes an airlock to help maintain the humidity. He also provides Francine with a giant tome of rules over who can enter the home and turns the proceedings over to Guunther, his property manager, noting at first that he has to attend to Grumpy Cat's cavity, and then when it's pointed out that Grumpy Cat is dead, saying that he's attending to his mistress.
Guunther, who is really one of Roger's personas and jealous that he didn't get the real estate job, tries to sabotage Francine by refusing to show the house to any of her potential buyers. However, she finally outsmarts him by selling it to another one of his personas.