What time is it? Sometimes the only way to know how many years have passed since you last looked up is to examine the current state of nostalgia. I distinctly remember a period in the mid-1970s when the earliest batch of Baby Boomers suddenly found themselves all grown up and began obsessing fondly about watching “Howdy Doody,” sparking a minor revival for the early 1950s TV show.

About 10 years later, Paul Reubens, a distinctly unique performer, created a childlike character named Pee-wee Herman and soon had his own thoroughly post-modern and oh-so-mid-’80s sendup of a kid’s show. Now, round about a quarter century later, the little ones who “screamed real loud” at his antics and magic words can return to their youth with the broadcast of “The Pee-wee Herman Show Live on Broadway” (9 p.m., HBO).

Reubens returns to his signature role and Lynne Marie Stewart reprises Miss Yvonne (“The most beautiful woman in puppetland!). John Paragon, also on the original TV show, appears as the disembodied head of Jambi the Genie.

It’s hard to believe how many cult figures or later-to-be-famous performers appeared on the original Saturday morning show. S. Epatha Merkerson (“Law & Order”) played Reba the Mail Lady, and Laurence Fishburne (“CSI”) was Cowboy Curtis. The late Phil Hartman (“The Simpsons”) was the original Capt. Carl. The late Shirley Stoler (“Honeymoon Killers”) appeared on that show as the mean Mrs. Steve. Even Jimmy Smits (“Law & Order”) showed up briefly as a robot repairman.

The set design for this stage version is based on graphic artist Gary Panter’s deliriously over-the-top approach for the TV show, and many of its anthropomorphized characters, including Chairy, Conky, Globey, Pterri the Fish and the Flowers and Magic Screen return.

Like any exercise in nostalgia, it’s hard not to watch all this and get a little wistful for the era of “Max Headroom,” Bartles & James, Fawn Hall, “Walk Like an Egyptian” and Joe Isuzu. The 90-minute running time reminds us how the original “Playhouse” was just about perfect at a half-hour. So is this worth watching? Not to give too much away, but tonight’s magic word is “fun.”

Tonight’s other highlights

• Overlapping coverage of NCAA Basketball Tournament (5 p.m., TNT, 6 p.m., TBS, 6:30 p.m., CBS) continues.

• A winner takes possession of a Vermont lodge on “HGTV Dream Home Giveaway 2011” (7 p.m., HGTV).

• A journalist (Richard Thomas) travels in time to confront his past self in the 2011 fantasy “Time after Time” (8 p.m., Hallmark).

• Male immaturity looms large in the 2010 comedy “Grown Ups” (8 p.m., Starz) starring Adam Sandler, Kevin James, Rob Schneider, Chris Rock and David Spade.

• Scheduled on “48 Hours Mystery” (9 p.m., CBS): college students cheat death in a creative fashion.

• Jo Brand appears on “The Graham Norton Show” (9 p.m., BBC America).