Mahou no Tenshi Creamy Mami

These two anime feature a young girl who can transform into an older, beautiful idol with the help of two magical creatures. The girls in both have certain restrictions on their powers. The style of the anime has a happy feel, but Full Moon includes a touch of tragedy.  

Both series are about a girl who gets magical powers, both have talking cats, and both contain romance. 

Fancy Lala and Creamy Mami are both Studio Pierrot Magical Girl series about young girls who are given the power to transform into an older girl and become idol singers. Lala is sort of like an updated version of Mami 

Both are about young girls who get magical powers to become older teens. Both have weird alien "pets." Both were made in the '80s. Both Mami and Persia like older boys and become older people in order to make them fall in love.  

Both are space themed magical girl series. Although Creamy Mami has idol elements thrown in too. I think people who love Star Twinkle Precure will find similar enjoyment in Creamy Mami.  

in my opinion, many of the magical girl shows of the 80's were like spiritual predecessors to the kirara-kei/cute-girls-doing-cute-things genre that blew up during the 00's. before sailor moon left its all-encompassing impression on the magical girl genre, magical girl shows like creamy mami were often devoid of the near battle-series nature epitomized by sailor moon. instead, many of this era's magical girl anime would focus on cute, nichijou-kei/slice of life stories where the stakes were often very low and the episodic adventures of their characters made for spectacular levels of moe. creamy mami and k-on are similar in that the magic possessed by yuu in creamy mami only really serves to transform her into a beautiful pop idol. due to their kawaii day-to-day scenarios and their focus on performing musicians (as well as the absolutely stellar animation in both), the viewing experiences of the two shows are surprisingly similar. read more 

Both series deal with idols, although the difference is that Creamy Mami has magical girl elements and is very childish, while Idol Densetsu Eriko is more dramatic and a bit adult. Without a doubt, both are highly recommended.  

Both include magical girls who transform into older girls. 

Both are super cute Studio Pierrot Magical Girl series from the 80's featuring heroines who are given the ability to transform into an older version of themselves and end up having fun and cute adventures. Emi becomes a magician, Mami becomes an idol. 

Both are Idol Animes with very catchy and nice tunes. Both feature a light purple haired protagonist that grows up when she's an idol. Both feature cute stuffed animals that talk. Both are really heartwarming shows ♥ ! 

Pretty little girls who use magic to transform theyself into successful charming idols, and sing beautiful songs that capture the hearts of the people. They have to keep their secret identities hidden, and there are also familiar magic pet for each girl. All the main girls are in love with a cute older boy.