In addition to "light?" Lucas is now trying to say "tree?" and "chickens."
Why "light" and "tree" are interrogatives, I know not. But "chickens" is apparently exclamatory.
The problem, however, is that he's only attempting the first syllable, and he doesn't have the hard "ch" sound down yet. So instead of "chicks!" we get "shith!"
Add that to his fake sneezes shtick and he's going to be the belle of daycare.