Not all of those are square pegs.
Is that necessary? I just wanted to use the peg-in-hole theme to illustrate the types. How does each type respond to the 'fitting-in' theme? Some types just do fit in...
But anyway:
That's what
SHE said!
Hahahahahahaa, "trying out all the holes", my mind immediately thought dirty things as well.

. Probably you won't believe me, but I only realised the dirty association after I read this comment.
In my defense, English is my third language (though by now I know it better than my second one). I don't know all the meanings of all the expressions.
Wouldn't "peg in hole" have a dirty meaning in all cases, then? Or only in the "trying out all holes" case?
I meant the hole as a metaphor for your place in life, eg job, family, home, neighbours,... Isn't that the meaning of the hole in the "square peg in round hole" expression? Some people just seem to fit in from the first try. Others never fit, despite all well-meant trying from our extraverted Guardians. Some carve their own place (ENTJs rule!)... Some try out all sorts of lives. Happily living one life doesn't mean you can't try out another, does it? And "trying out to look for the best possibility" seemed something an ESTP would do.
I'm not sure which type this is best suited for. I'll leave that up to you all...
Pretension
Yeah, ENTJ seems to be the one

And I've got this feeling there is some truth in the caption. What if you're
really better and more succesful? Wouldn't others call you pretentious, just to console themselves that there is fault with you, too?
At least in my country, it's good manners that when someone compliments you with "you're good at..." you answer with "but I suck at..." Never stick out. Never be good at more than one thing at the same time. Never say "look, I'm good at this!"
ENTJs won't keep their talents hidden just because it's good manners to do that. And that's a good thing.