I have an amazing take from 1996, please listen - Yoosung Kim from Mystic Messenger and Mallow from Super Mario RPG are essentially the same person. There is an unnecessarily long list of supporting evidence-y items supporting this claim under the cut!
They are both highly and openly emotional. Both characters are sobbing when we meet them in the story and afterward cry so frequently/powerfully that it's a defining character trait.
Both also have character arcs in which they start off as immature, with low self-esteem, and without direction in life, but become courageous, motivated and strong by the end of their journey
Both characters' lives are profoundly impacted by absent family member/s
Cute bangs
Raised by someone with conservative/traditional values
Both are distinguished in their parties with a light green symbol (Yoosung gets the light green heart, Mallow's magic spells are proceeded by a light green ♣)
Both are gullible
Light blue clothes
Uhhhh if you want to count Mario's unreal miming skills in SMRPG, then I guess both Yoosung and Mallow have someone in their life who strongly reminds them of someone else
Both are raised by the water¹, and with hard work, take their place in the SKY
Mallow has healing magic, Yoosung studies medicine
Money problems
Both favor striking weapons (Mallow's froggie stick, Yoosung's giant hammer in LOLOL)
Both have parents with government jobs
Out of the men in their party, they are the shortest. Out of all the party members, they are physically the weakest (Considering Mallow's Attack stat is lower than even Toadstool's, and the fact that Jaehee does judo and probably has the edge on Yoosung there)
Although there are no canonical ages for the SMRPG party members, I think it's fair to infer that Mallow, like Yoosung, is also the youngest party member (with respect to Geno's age as a star rather than his time 'living' as a doll)
Both have relative/s who were in charge of a group of people. A artistically inclined green(ish) haired person lies about the health/wellbeing of Yoosung’s/Mallow’s relative/s, and assumes authority over the group. The RFA and the citizens of Nimbus Land both accept the lie, but Yoosung and Mallow persist in skepticism of the usurper's claims
(Why yes, I did just compare V to Valentina. Let that mental image marinate in your head.)
Bus rides
Both defeat dragons, with the help of teammates
Omelettes are fluffy, much like Mallow. (Also with regards the MM April Fool's event, you could also argue that both characters have a reason to dislike birds)
Both of them have a struggle with a switch toward the end of their stories
Mallow has a spell that summons a falling star, FFS
¹Yoosung Kim went to school at Seaside High School, as indicated on his Student ID Card in Cheritz's 'Special Believer' Mint Eye Package
