Both #らーめん and #らーぬん hashtags lead me to ramen posts. I'm aware that Ramen is called #らーめん. But what is #らーぬん?
Legend has it that a long ago, a prankster saw the sign that read 「らーめん」 in front of a tiny restaurant while walking down the street.
"What a boring sign! Think I'm gonna spice it up a bit.", thought the prankster. He took his permanent marker out of his North Face backpack and changed the hiragana 「め」 to a 「ぬ」 on the sign. "らーぬん! Damn, am I creative!", he murmured.
Two days later, the dude decided to go check the sign that he had worked on. The sign had been re-painted in katakana this time -- 「ラーメン」. "The owner must have thought that would prevent the same kinda prank from happening again. Is he kiddin'?", the prankster said to himself, shaking his head. With a marker, he quickly altered the 「メ」 to a 「ヌ」 this time. "ラーヌン! That's much better!"
Incredibly, this two-kana-system-cat-and-mouse game lasted over six months until the owner finally decided, in distress, to take the ramen out of the "メヌー" (Pun #1). Needless to say, this historical incident took place in Hirakata, Osaka (Pun #2).
Note: I admit unwillingly that the last paragraph is my own creation, but the rest of the information is all over the internet if you search in Nagoya dialect.