Has anyone had any luck with these toppers designed to perch on the edge of the cake? I've heard some scary disaster and near disaster stories. I had hoped that some royal icing would hold it in place on a fondant-covered square cake but maybe I need a plan B? 
Any and all advice appreciated! 
I had to put the sitting couple on a square stacked cake the other day. It actually was cute, peeking out around all the flowers. Cake was fondant covered with good sharp edges for a nice "perch" for their butts. I did put a dab of RI on for security. And added it on at the end once it was in place on the cake table. I don't know why it would be scary. There is plenty of room to work with, as far as how far out their legs stick versus how far back their butts sit. Make sure your cake is flat and smooth and level, and you wouldn't even need RI.
No royal icing won't hold them....I did one a couple of months ago. That thing was HEAVY and it was not balanced correctly. I HATED it. I didn't even get a pic of the side with the thing on it, I took a pic of the BACK of the cake (and I am hoping the photographer did too) I had to put dowels in the cake under where it was going to set - and watch the feet - they like to dig into the cake when you are putting it on. 
NOT a fan of them at all.
The one I had was made of ceramic and their legs went backwards some - there is NO way it would have set on the edge of a cake and stayed without support.
What a relief! I thought it would be OK with royal underneath and maybe even a bit on the back of their legs but read a few stories on other forums where the couple fell off the cake at one point. I'm glad to hear that it's been used successfully! 
Thanks very much for the replies!!
I guess I was referring to the gumpaste ones we make ourselves....but then I guess they fit the side of the cake better than the ready made ones? I would think the ready made ones would be lighter weight though...?
I've done the baby shower cupcake towers where I made a figure perch on the side of the topper cake and the royal holds them great all through delivery and everything.
I don't know where the bride got the topper she used, it wasn't like the ones you have posted pics of (both OP and _jaime_) It was not balanced - and the feet were made wrong - if you set it where it was supposed to be, the grooms feet dug into the side of the cake. Leave it to me to have the screwed up one for the cake I do.
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