Every anime fan becomes accustomed to suspension of disbelief. Once we learn and accept the logic that runs a particular show, we can enjoy it without becoming hung up on little things. If we can't believe in the logic, we may as well abandon the show for something more realistic... and most of us don't center our entertainment on 2D Japanese shows because we're looking for realism.
Five school idols all fall for a plain, normal girl? Sounds logical.
A kid eats a fruit and becomes the stretchiest pirate around? Sure! Why not?
An orphan boy is allowed to live all by himself from a young age? Makes sense.
Middle school kids have tennis moves an Olympian would envy? Okay.
Ninja and other fighting pros yell out their moves before doing them? Of course!
The crazy bunny, the penguin, and that other talking creature are Chimera Ants? Alright, if you say so... though they really don't look at all like ants to me.
Chimera Ants in episode 82 of Hunter x Hunter
It would be easy to criticize whoever came up with story and character design for expecting us to swallow some of the outlandish things they pull... but like I said, chances are that few, if any, of us came to anime because we wanted reality. It's escape, a place to be enveloped in fantasy, whether that fantasy is wrapped as unlikely romance or shounen action. If you want reality, feel free to flip on the news. Personally, I'm going to stick with my Chimera Ants.