TUNED IN

She’s young. She’s emotional. She’s talkative. She’s a bit of a ditz on the street but canny in court. And she’s stuck working with a man she used to love. She’s ... Jenny Shaw, the newest member of the Boston law firm of Cage/Fish & Associates.

Are you ready for Ally McBeal, mentor?

In a strange twist befitting the reputation of creator David E. Kelley, “Ally McBeal” launches its fifth season tonight (9 p.m. Fox) with Ally (Calista Flockhart) suddenly acting grown-up and playing big sister to Jenny (Julianne Nicholson), a near clone of the Ally we met in 1997--right down to working with a former boyfriend, Glenn (James Marsden), another new hire at Cage/Fish.

“Ally” is getting a make-over--both the show and the character. Gone are roommate Lisa Nicole Carson and lawyers James LeGros and Taye Diggs. Gone too, at least tonight, is Ally’s spunk. Her hairstyle and general appearance radiate newfound maturity.

Having been abandoned by her lover at the end of last season, she clearly is feeling older if not wiser, especially with these younger folks in the office.

But not too old to have a strong interest in Glenn herself....

Yet here’s how different this “Ally” is. Remember the season-opening episode in 1999 when Ally had sex with a stranger at the car wash? (How could we forget?) Well, her intimation of sexual desire tonight brings only an admonition from her new therapist (John Michael Higgins) that the means for remedying it lies in her own hands. Literally. How unromantic is that?

And get this: There’s a plot point that turns on an overheard conversation--but not in the office bathroom!

Whether these efforts at formula busting will be for better or worse is impossible to predict. “Ally McBeal” has always been as creatively erratic as its heroine’s hormones.