Hitting the undo button will cycle you back through all of the tile placements you've made.
If you're really stuck for space it's no problem to place tiles next to each other, as long as they touch by a corner diagonally. Only tiles that directly border each other can interact.
If you're struggling to eke out those extra drops of happiness in a level, sling a few nerds into the corners of a grid. You can get double the happiness rating by placing a nerd on a corner, as this will expose him to two different edges.
Nobody likes burning their bottoms while out on a picnic. When you're presented with such a situation, pop a cake onto a sizzling patch where possible - cakes really don't like to complain and everybody stays happy.
The optimum number of girls to have around any single robot is three.
June loves bugs, but bugs will flee from the usual girl tiles. Drag a girl tile towards the bug, but don't let go immediately! If you hover the tile over the play area, you'll get a preview of how the bugs will move. Use this to tease the insects towards June.