As we all know, 50% of my DNA is the same as that of a banana; the odds are good that 50% of your DNA is also the same as a banana (assuming all three of us shared the same common ancestor). I've referred to this elsewhere.
The thing is, this is true of all fruit, vegetables and plants. So why are bananas singled out?
There's something about bananas that people identify with. If I said "You share 50% of your DNA with a potato", it sounds like an insult. Bananas are yellow, funny, hold easily in the hand, come with their own wrapping and have a long an honourable history in slapstick. It may not be a compliment, but it's not derogatory.
When I was younger I couldn't get enough of bananas. I was served mashed banana as pudding all the time as a baby, and later I loved bananas in custard. Plus, you can use it as a gun, or shake hands with a bunch. There was a garden centre with a greenhouse somewhere in Scunthorpe, which we went to all the time and it had a banana tree, which was always growing a bunch of bananas. That greenhouse was hot, steamy, exotic and had a banana tree in it! I also loved monkeys at the time, and my ambition was to be a monkey and live in a greenhouse with a banana tree.
Since then I've gone off bananas a bit, but I still have some affection for them.
Update: I meant to mention the Marvel What-If comic mentioned in the linked to comments thread which was "What if the Fantastic Four were fruit?". The only what-if I'd rather see is "What if Bruce Wayne were bitten by a vampire hat?"
 Maybe not mushrooms.
 Also monkeys.
 Or, as this would be a DC comic, an "elseworld".