In general, Pit is not so much super stupid as tremendously naive and lacking any brain->mouth filter, while Palutena has a cynical undertone and Viridi is an openly sarcastic brat. Pit also frequently likes people who show themselves to be badass.
Pit: This guy is SO cool! After this fight I wonder if I could get his autograph?
Viridi: Ugh. Really? He's just a jerk in a suit and a stupid helmet.
Pit: Don't diss the helmet! I think it looks great. Very heroic.
Viridi: And he has NO imagination. Seriously, "Falcon Kick", "Falcon Punch", "Falcon Rise"...? Grow some variety already! And who calls out their attacks anymore? What is this, the eighties?
Pit: This from the person who made up "Bumpety Bomb".
Viridi: HEY! Bumpety Bomb is an ADORABLE name!
Pit: Wow, she's good. Especially for a human.
Palutena: That's Lucina of Ylisse, Pit. She fought a hopeless war for years and prevented her country from being taken over by the hordes of Risen, and even came back in time to save her own father and the world. So you could say she has almost as much combat experience as you do.
Pit: That is pretty awesome. And she's so pretty. I, um, wonder if she'd want a hand with the undead thing?
Palutena: Oooooohhhhh, is that a note of infatuation I hear in your voice, Pit?
Pit: What?! O-of course not!
Viridi: Pit's got a girlfriend, Pit's got a girlfriend!
Pit: I DON'T-!
Lucina: Your fighting seems off. Is anything the matter?
Pit: Gah! N-nothing! Nothing at all! I'm perfectly fine! Just enjoying a fight here, haha!
Lucina: Good. I am also enjoying this spar. You are a fine swordsman, Pit.
Pit: R-really? Thanks! I-
Lucina: Now, en garde!
Pit: UWAAAHH!