I've been trying to find an alarm clock made out of a potato...

I've been trying to find an alarm clock made out of a potato...
...ever since I had a meeting with my boss about arriving late for work and he told me "Get a potato clock".

This is a mondegreen (which is a phrase that sounds similar enough to another phrase that the two can be confused for each other). The thing that the jokesters boss actually said was probably "get up at eight o'clock", but somehow the jokester heard "get a potato clock" instead.

All mondegreens are misunderstandings, so this is also a misunderstanding.

This misunderstanding isn't really likely at all -in fact I would consider this joke to be entirely unbelievable and pretty terrible personally.

The most likely reason to laugh at this joke is because it is so bad.

I would consider this a dad joke.