Adding infant brother Jamie to ''Malcolm in the Middle'' in the fifth season hasn't stopped the other siblings from acting like babies. On the recent Thanksgiving episode, Reese (Justin Berfield) stole $80 from his father's wallet to pay for cooking ingredients, Dewey (Erik Per Sullivan) was commanded by Reese to ''turn on the cute'' to con store clerks out of truffles, and a visiting Francis (Christopher Masterson) bawled over his wife Piama's (Emy Coligado) threats to divorce him (they had a big fight after she wouldn't let him drive drunk). It was all a reassuringly dysfunctional holiday scene at the house...until a flirty classmate came on to an inebriated Malcolm by tossing him a condom.
What? The boy we saw struggle through his first kisses is now fielding rubbers? It was like seeing ''The Family Circus''' Jeffy take his first bong hit. This jarring ''O.C.'' moment was all the more discomfiting as it came in a season that has mercifully toned down last year's shrillness. (Finally, Jane Kaczmarek has more to do than just holler: Her quiet reverse psychology to get Francis and Piama back together was not only well written but Exhibit A in the case to get the young couple home permanently and away from that unfunny dude ranch.)
Now that the performances are back in check, ''Malcolm'''s most destructive family influence seems to be Father Time. Malcolm's character, a boy genius perpetually exasperated with his wreck of a family, hasn't changed. But at age 17, Frankie Muniz's perma-grimace -- displayed on his maturing, angular face -- has become off-putting. Ever since the series' writers phased out his school peers, the brilliantly awkward Krelboynes (leaving just the wheelchair-bound Stevie, who may need an upgrade to a wheel-SUV thanks to actor Craig Lamar Traylor's even more transforming growth spurt), Malcolm's just like any sullen teen you can see slouching and eye-rolling at malls across America. It's now Dewey and his hallucinatory obliviousness that provide the loopiest moments, like his bedtime story to Jamie about a magical closet that holds the ultimate treasure: a pair of pants that aren't hand-me-downs. But at 12 years old, Sullivan is on the precipice of puberty, and soon such fantasies will only make him seem like a half-wit.
The inevitable reality of aging child stars is unfortunate, as ''Malcolm'' still amazes with vibrant comic creativity. The season premiere -- a trip to Vegas featuring a delightfully egoless David Cassidy crooning ''Papa Don't Preach'' to pregnant showgirls -- didn't come off as pure stunt thanks to the crazed performance (and skilled direction) of Bryan Cranston (Hal). And thankfully, creator and exec producer Linwood Boomer has so far avoided using little Jamie for his awww factor. Instead, the tot showcases the family's irresponsibility: In one instance, Reese fashioned a diaper out of newspaper and an oven mitt. But Jamie may also end up being a necessary writers' tool to stockpile childhood as the core kids get older. And if, in the future, he ends up taking camera time from the brothers, well, as the show's theme song says: ''Life is unfair...''