Game play is different on the PC version to the console versions (xbox, ps3, wii). Most people on the forum play the PC version, so they don't have the answers to console questions. Which is why they have the console board forum, as it's easier for other console players to find people's questions.
Your child has the "immune to fire" trait (or firebug trait, something like that). It comes from a firefighters genes, if a parent or grandparent was a firefighter, they can pass this hidden trait to the child. I haven't played console for a while, but I recall the transmogrify would turn a seed or fruit into a flame fruit seed or flame fruit. Your sim can start fires, also, sometimes if you click somewhere the option "start fire" or "burn this" or something like that pops up, and I am pretty sure they are immune to fire as in they can't burn to death.
