1) Star-Lord/Peter Quill
There’s a reason James Gunn cast Chris Pratt 30 seconds into his audition, and it’s his organic ability to provide off-the-cuff improvisational dialogue. That personality matches Star-Lord/Peter Quill to a tee, but it also enhances all of the actors around him.
Chris Pratt is kind of like a rug that ties your living room together, except he’s the backbone to the Guardians Of The Galaxy. It’s abundantly clear that a lot of the comedic touches to the film work due to his seemingly natural camaraderie with all of his fellow Guardians. There is an infectiously witty presence to him that you just can’t get enough of.
He is also the viewer’s link to the galaxy. It’s not just a style choice to have Peter sentimentally listening to 80s music that remind him of his mother, it’s something that we the audience can use to connect themselves to his world up in space. Deep down, Star-Lord is Peter Quill, a dude from earth just like us, except he’s caught up in a cosmic adventure. And through him, we are able to relate to the rest of the insanity.