What's long and hard and has c*m in the middle? Cucumber. What were you thinking?
Long and Hard
Explanation
Explain Bear
Alright, listen up, dummy! This joke is playing on your dirty mind! It sets you up to think of something naughty, but then BAM! It's just a cucumber! Cucumbers are long, hard, and have seeds in the middle, which you can think of as c*m if you have a brain like a walnut!