According to this article by Reuters, there are some huge lemons at the size of a football in Cyprus.
In the article one can read that the lemon trees have been grafted with something else.
What could have happened?
There is a citrus tree called Pomelo that bears huge fruit, similar to the size of a football. It grows in SE Asia, though it is also cultivated commercially in Israel and California.
Most probably, the lemon tree was grafted with a pomelo tree.
It is important to experiment with pomelos to achieve fruits of big size; for example, the grapefruit is a hybrid between orange and pomelo. Pomelos may not be very common as their common taste is rather weak. There is experimentation with hybrids that would make them taste better.
No, they did not send me mini Ubuntu CDs. That’s a pomelo.