Damnation!!!!!!!!!!

we'll start with the obvious. as residents of earth we think of gravity as a downwards force. gravity man's design is full of downwards movement. gravity is a big fucking dorito. you may have noticed his record-breaking shoulders. perhaps the triangle on his helmet. his triangular shape language gives the impression he's pointing down towards the earth. in addition, gravity man's big fucking shoes, which look reinforced with those yellow bands, and with midsole lines that are usually only seen on bigger rms like stone man, give the sense that he's seriously digging into the ground from the force of that downwards movement.

gravity man is wearing a belt reminiscent of a wrestler's heavyweight championship belt. even aside from the name, these things are known for being HEAVY!! (up to 20 pounds ish). weight is defined as the downwards force on an object due to gravity (mass x acceleration from force of gravity). this is an extremely cool and clever detail

gravity man is very apple flavored. he is shaped kind of like an apple slice. he is colored like an apple (reds, greens, creams/yellows). he is newton's apple. (and he also explicitly references newton in his smash bros ultimate dialogue fun fact!)

gravity's metal hat thing looks a lot like slotted masses. slotted masses are basically discs with set masses that you can put on a weight hanger. discs with different masses have different sizes. they're often used in physics experiments! (for testing forces and whatnot... such as gravity). given how spark's helmet is a spark plug, i'm inclined to believe gravity's helmet is also supposed to reference a specific thematically-fitting object.

5. my guess is that the thing in the middle of gravity's chest is supposed to be an analog multimeter, a tool that can measure voltage/current/resistance (also used very often in the physics experiments he loves so much). (EDIT: if it IS an analog multimeter, those two wires he has on his hips could also be part of it.) Alternatively it could be inspired by analog weight scales. either fits! Or it could be a reference to some other type of analog instrument meter i just don't know about.

6. finally, gravity man is a physics researcher whose stage takes place in a gravity research lab. i LOVE how his design looks like it came straight out of a zany american kid's science show from the 80s. the tubes on his stomach. the analog meter on his chest. the hammy "G" on his belt. all of these comically extraneous details actually come together to sell a "gadgets and gizmos" aesthetic! it's a really unique and fun way to emphasize the "science" angle!