It says "all right / but... / does causation imply correlation?".
Why it is funny: because there are so many memes and epic examples about how correlation DOES NOT imply causation, and almost none wonder if the implication works the other way round (well, some people do on forums like here and there is still some debate).
This one is quite popular too. I guess my T-shirt caused the scientific community to work on this question.
This T-shirt is made with 100% coton, ringspun technology. It has an exceptionnaly high thickness, making it both robust and pleasant to wear. The design is manually head-transfered to the fabric via the flex technology. This T-shirt can be washed inside-out at 40°C. No tumble dryer. If you damage the printed layer by accident (or tumble dryer), iron it through a parchment paper to smooth it again.