From the Super Mario Wiki
Joke's End is a frozen palace in the Beanbean Kingdom. The only route to Joke's End is via surfing the Oho Ocean or by using a warp pipe. Mario and Luigi traveled to this palace during the events of Mario & Luigi: Superstar Saga. Joke's End is inhabited by Jojora and her friends, and, although one line of dialogue stated by Jojora ("I'm the buddy of the cousin of the descendant of the spirit who once guarded this palace") suggests that there is or has been more people living in Joke's End, they seem to be its only occupants (although one Beanish character, presumably a visitor, is seen on a staircase of it). Joke's End is also known to be a graveyard for bad jokes, though none of these dead jokes are actually seen. This ties in with the theme of locations in the Beanbean Kingdom being named after laughter sounds (Chucklehuck Woods, Teehee Valley, Guffawha Ruins, etc). During their trials in Joke's End, Mario and Luigi often had to split up to solve certain puzzles, making Joke's End arguably one of the hardest destinations in their adventure.
The palace is made almost entirely of snow and ice (due to the cold reaction bad jokes get), making it resemble the Crystal Palace from Paper Mario. Its design includes several statues of Beanish-type characters giving horrified looks; these monuments may be headstones for the palace's aforementioned and unseen dead jokes.
The final Warp Pipe in the game, #9, is located at the entrance to Joke's End.
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