what goes around the world but stays at a corner
A stamp? :)
Space station mushrooms. :-)
http://blogs.abcnews.com/scienceandsociety/2008/11/mushrooms-in-sp.html
The answer to the riddle "What goes around the world but stays at a corner?" is a stamp. A stamp goes around the world when it is placed on an envelope and mailed to different destinations, but it always remains in the corner of the envelope.
Riddles like this can be fun to solve, and you can often figure them out by thinking of different objects or ideas that could fit the given description. In this case, by considering things that can go around the world but also stay in a corner, you can come up with the answer.