odd couple; mismatched pair
Refers to a duo (often in entertainment, sports, or work) whose personalities, appearances, or styles contrast sharply, creating a humorous or striking combination.
The comedy routines of that odd-couple duo are always funny.
He's tall and she's petite, so they look like a mismatched pair.
Compound of 凸凹 (でこぼこ, 'uneven, bumpy') and コンビ ('combination, duo'). The word 凸凹 is a native Japanese term, while コンビ is a loanword from English 'combination'.