ha! Well its more that each of these characters are dressed clothing goku had himself wore at some stage. Anger's clothing is the same as when goku became ssj for the first time.



It was fortunate goku did wear saiyan uniform at one point because it fits disgust so well given that gear is associated with vegeta AND HIS SAIYAN PRIDE! Or just saiyan pride as a whole, goku included.



Sadness is wearing goku's clothing when a kid (I had a much earlier draft of her holding a grandpa gohan doll)



Joy is self explanatory, it was by good chance that goku was much more cockier giving justification for joy to be at centre of controls again, as well as the blue connection of course!



As for fear, he was the hardest one to sort out, there isn't much of goku's past clothing that could be tagged with fear, but caution, and need do develop from fear and goku (knowing he dislikes work)t does it because he knows his family depends on it. So I took that clothing from Dragonball Super. One could argue that farm work is the equivalent of office work for goku.