If you liked the Assemble Insert anime, the Anime-Planet community thinks you'd like:
Hiroshi Ozora has always wanted to be a superhero, so he decided to do the only logical thing: create a transforming power suit called Moldiver! With it, he can fight the forces of the maniacal Professor Machinegal, who desires all of the rarities of the world for his private collection - but when his sister Mirai accidentally changes the suit's design to that of a beautiful girl, Hiroshi's plan goes terribly awry! Now, Hiroshi and Mirai must share the suit, alternating between manliness and beauty, to put a stop to Professor Machinegal!
Moldiver and Assemble Insert are both light-hearted looks at an ordinary person who has been given extraordinary powers. Assemble Insert is far more humorous and entertaining, but fans of one should probably enjoy the other.