impersonate, dress up, disguise, thin shingles
扮 centers on changing one's appearance to become someone or something else: impersonating, dressing up, or disguising oneself. The rare 'thin shingles' sense is a separate, unrelated meaning.
扮 combines 扌 (hand) with 分, which likely contributes the sound and the idea of dividing or separating, perhaps suggesting using the hands to change or divide one's appearance.
The hand radical 扌 beside 分 (divide) suggests using your hands to divide or change your appearance: dressing up or impersonating someone.
For フン, imagine a fun disguise: fun -> フン, and your hands are busy dressing up.