The terror threat remains deadly serious. But the aura of reverence and awe that surrounded the subject has taken a back seat to frustrations over long delays at airports and qualms about the cost of the bureaucratic leviathan that is the Department of Homeland Security.

The new documentary series “Homeland Security USA” (7 p.m., ABC) hopes to put a human face on the folks who patrol vast stretches of the U.S. border, who scan countless packages at airports, seaports and international mail centers and who monitor “chatter” in cyberspace.

Apparently, there’s no better way to demonstrate the deadly seriousness of an endeavor than introducing a little quirky humor. We see tiny toys shipped in from Cambodia stuffed with narcotics. And toys are the least of it. Diapers are also a smuggler’s best friend.

A package of suspicious “meat” is actually an Asian delicacy — roasted bats. And we also encounter a Swiss miss who was casual enough to travel without a passport. Could it be that she’s distracted by the curious contents of her luggage?

The hidden camera point of view may hearken back to “Cops,” but the no nonsense, we’re-just-doing-our-job-under-difficult-circumstances atmosphere is pure “Dragnet.”

Only with so many documentary police series springing up all over the network and cable dial, (See “Vice Squad” 8 p.m., MyNetwork, premiering tonight) you have to wonder if they’ll ever produce a scripted police series again.

It’s getting hard out there for actors. We might be preventing the children of tomorrow from ever discovering an Erik Estrada to call their own.

• The new series “Wreckreation Nation” (9 p.m., Discovery) scours America for unusual contests like lawn-mower racing, fruitcake chucking and catfish wrangling. Dave Mordal (“Last Comic Standing”) hosts.

• “Scrubs” (8 p.m. and 8:30 p.m., ABC) makes some major changes as it enters its eighth season. Courteney Cox appears in three episodes, and the sitcom moves to a new network. “Scrubs” is still not as funny as it thinks it is.

• “Independent Lens” (9 p.m., PBS) presents the 2007 documentary “Helvetica” a history of and cultural and political discussion about the most commonly used typeface of the late 20th century.

Used on everything from tax forms to Coke ads to the Beatles’ “White” album, Helvetica has many meanings as it has detractors. It is also so ubiquitous as to seem invisible, and that is what some believe gives it power.

Tonight’s other highlights

• The celebration of The Three Kings takes center stage on a special episode of “Dora The Explorer” (7 p.m., Nickelodeon).

• Jane quits the bureau to investigate a possible clue about his family’s killer, “Red John,” on “The Mentalist” (8 p.m., CBS).

• Secrets from Thirteen’s past emerge on “House” (7 p.m., Fox).

• “Dirty Jobs” (8 p.m., Discovery) enters its fifth season with a visit to a bologna factory. Or is that baloney?

• A rapidly spreading virus endangers an FBI agent on “Fringe” (8 p.m., Fox).

• Scheduled on “Frontline” (8 p.m., PBS, check local listings): “The Old Man and the Storm,” a film following 82-year-old Herbert Gettridge and his extended family as they cope with the aftermath of Hurricane Katrina.