Double Takes

Watch a television hero’s “evil twin” at work on a science-fiction or adventure series, and you’re bound to find a pretty despicable character.

Sitcom look-alikes are a different story. They’re usually only mischievous or, at the very worst, obnoxious.

Patty Lane is usually at the very worst. She’s the impulsive, all-American, self-centered teen-ager on The Patty Duke Show (weekdays at 11:30 p.m. and weekends at 4 a.m. on Nickelodeon ). Cathy only looks like Patty; she’s her sensitive, considerate Scottish cousin who lives with Patty’s family.

It is indeed possible that you can lose your mind if you try too hard to figure out how cousins can be two of a kind. (Save your sanity by assuming that their look-alike dads have some pretty heavy-duty genes).

Patty Duke, who had just won an Oscar for 1962’s “The Miracle Worker,” played the Lane cousins from 1963-66; Rita McLaughlin “starred” as the back of Patty/Cathy’s head.

Other sitcom twins cause trouble this week when: Samantha splits Darrin’s personality between two look-alikes on Bewitched (Thursday at 8:30 p.m. on Nickelodeon); Oliver is suspected of hanky-panky when his double is seen kissing another woman on Green Acres (Friday at 9 p.m. on Nickelodeon), and Alice’s cousin Emma, an ex-WAC, takes over The Brady Bunch (Sunday at 6:05 a.m. on TBS).

The most evil set of twins of the week is played by Liberace, on a two-part Batman (Saturday at 2 and 2:30 p.m. on KTTV). The Liberace episodes were the highest-rated of the series.