Duolingo Japanese is very healthy
A Duoりんご a day keeps the doctor away!
Somewhat true, but you could say, "A lesson a day keeps ignorance away."
Excuse me, but it looks I'm a spanner :D Do you mean that Japanese is a good training for brains? If so, why exactly Duolingo Japanese is healthy, is it some special sort of Japanese? I thought you gonna keep your brains in good form wherever you learn it...
He made a pun on the saying "An apple a day keeps the doctor away" since apple and lingo both translate to りんご.
Joerice01, using hiragana emphasizes that it is a pun on the word "apple". Otherwise, people would be more likely to read it as "lingo" instead of "ringo".