There's a bit of a story behind these guys. My daughter, Tilly, is 2.3 years old, and has always been fascinated by my MOCs. Long story short, she's been playing supervised with my LEGO, and always wants me to build robots for her. At first I built robots that appealed to my tastes, but they just didn't stand up to a two-year-old's active play. So after a couple-dozen revisions, these guys were the result.
They're colourful, characterful, relatively robust (the legs and arms stopped coming off some time ago) and now form a little happy family unit, in my daughter's eyes at any rate!
The moral of the story, it's actually quite challenging coming up with MOCs that are fun AND friendly to smaller kids. I've loved the process though!
More images here: http://www.flickr.com/photos/rg-b/sets/72157628287954203/