That was quite enjoyable! I liked the special effects in particular: both the "fog/explosion" effect, and also smaller things like putting on/taking off the sunglasses. The voice acting was done quite well (although the farmer's volume was noticably lower than the rest), and I liked the overall look and design of the film. It looks like your lighting setup is quite good, though there was some light flickering in places.
So since you're looking for feedback, a few things I think you can improve on.
First off, the camera angles. I've said a few things about that in my review on your newer film, Riddles in the Dark, but I think the flaw is more noticable in this film. Pretty much everything is filmed from a straight angle right onto the set, from a fairly far distance (wide shots). I really think your films will improve a lot in terms of cinematography if you would vary it up a bit more. Try to shoot from a 45 degree angle: this will help break up the monotony and make shots more interesting. Think about what you want to show and how to achieve that: when two characters are talking, get in a bit closer. It might help to rewatch a film you love and analyse how it's shot: how long is every shot? When do they cut to close ups, or wide shots? It also helps to draw out a storyboard before you start animating a scene. Don't be afraid to get creative! Even if it's hard to get the camera where you want it, it really pays off in the long run.
Something else that I think you can improve on is the way you tell your story. Let me take the castle/medieval scene as an example. Banana Man all of a sudden finds himself in medieval times, holding a sword and fighting with an unexpected enemy. After defeating said enemy, the people rejoice and promptly crown Banana Man and makes him their new king. (BTW, I loved that shot of the crown on top of the banana suit: not only is it genuinely funny, it also shows that you can change up the camera angles.)
So my gripe with it is that everything happens very fast: there's barely a build up to the fight scene, and there's barely a fight scene to speak of. By "build up" I mean that Banana Man doesn't really have a reason to do anything. Something simple before the fight, like a peasant saying "Banana Man, please help us defeat this evil tyrant!", would help establish to the audience that there is an evil tyrant. Now you have a fight between good and evil, rather than a random person attacking Banana Man. It also helps make sense that Banana Man is crowned afterwards.
The fight scene itself should (in my opinion) have been longer, too. Right now it's three hits and it's over. You could add some drama by choreographing the fight: what if the bad guy takes Banana Man by surprise, and before he knows it Banana Man is on the ground fending off his attacker? What if Banana Man uses his sword to disarm the other guy, sending his weapon through the air into the bushes? What if Banana Man gets disarmed, and as the other guy is trying to grab him, he can barely reach for his sword?
It's tricky and takes a lot of time to plan out, but it's worth it to get the audience on the edge of their seats. It also helps here to use camera angles: something like a close up of a sword flying through the air and falling into the bushes helps break up the action. Cutting back to a shot of the characters reacting to the action may pull the audience in more. You might want to look at (brick)films with fight scenes to get inspiration from. One of my favorite fight scene shorts is Fight by Errol, but there's plenty of other stuff out there.
I know it's a lot of criticism, but I do want to stress that overall I really liked this film. It's quite ambitious, and you've done a wonderful job. You should be proud!