Sometimes you have complicated feelings to express and the only thing you can think of to convey said feelings is a hamster dressed as a lumberjack. Go with your gut.
How are those letters coming, cuties? This is a serious stack of adorable here. http://stuff.icanhascheezburger.com/2011/07/29/cute-kawaii-stuff-lets-get-writing/
Robots are appropriate for any occasion. They are neutral but friendly so you can use this card for birthdays, get well soon, congratulations on your new baby, good luck on your exams, anything!
Tell that special someone that they're foxy! Tell that sneaky sly fox that you're onto their schemes! There's got to be a reason to send everyone a fox!
I'd prefer to write a note on a real leaf with a sharp stick, but that's just me.