Sorry for my nonsense post, but as a Dae Jang Geum fan and a Beatles fan I personally think it is interesting to cast any single Dae Jang Geum casts as The Beatles.
John Lennon: Jang Deok The reason why I think Jang Deok suits to be John Lennon is because John and Jang Deok have some similarities on their personalities. Jang Deok is similarly snarky and cynical like John. Jang Deok, just like John, also has some rebellious streak on her personality.
Paul McCartney: Jang Geum The reason why I think Jang Geum suits to be Paul McCartney is because Paul and Jang Geum are similarly bright, optimistic, and people-pleaser. Plus, Jang Geum is known to be the pretty one in the series just like Paul who is known to be the cute one in the band.
George Harrison: Shin Bi The reason why I think Shin Bi suits to be George Harrison is because Shin Bi is rather quiet and shy like George.
Ringo Starr: Chang Yee The reason why I think Chang Yee suits to be Ringo Starr is because Chang Yee is similarly light-hearted and humorous like Ringo.