A rough translation of "Mr" might be in "master." There is an invented word for "fluff," faskah; the word for "fluffy" would probably be faskahus. So, "MrFluffyFluff" would end up being "In Faskahus Faskah."

There's no literal translation for "mister", but "zoh" can be used as a title of respect, like "sir" and "madam/ma'am". "faskah" means "fluff", and from it we can derive "faskaheyd" to mean "fluff-like", "faskahus" to mean "fluffy", or we could use "faskiis": "fuzzy"

So, putting it together, "MrFluffyFluff" would most closely be either:

"zoh faskaheyd faskah": "sir fluff-like fluff",

"zoh faskahus faskah": "sir fluffy fluff", or

"zoh fasiik faskah": "sir fuzzy fluff"

***all of this is non-canonical***