Miss Martian is not exactly a rip-off of the Martian Manhunter, but is pretty close, essentially being a junior female version. She even uses the name Martian Manhunter in at least one timeline. She also poses as the Star-Spangled Kid of all people for some reason. Knock-off or not the character is a popular foil and bounces back with every reboot.
References: [wikipedia.org: Miss Martain]
[dc.fandom.com: M’gann M’orzz]
Metahuman Database 