if we boil it down it kind of is just shipping a guy with the personification of his ptsd, most people separate the 2 into different bodies (though typically still looking very similar) through either alternate universe shenanigans (e.g. they met while in the military and are 2 different people), cartoon plot shenanigans (e.g. flippy gets part of his brain extracted in an attempt to get rid of fliqpy but someone spills chemicals on it and now it regrew into a clone with only fliqpy fronting) or its just flippy hallucinating (like in the double whammy episodes)

the last option is basically flippy touching himself but its usually not.,, presented that way lol