“How I Met Your Mother” star Neil Patrick Harris is recording the voiceover for Listerine’s fun new educational short, “This Is Your Mouth,” and he’s spilling the beans on his highly anticipated appearance on “Glee”! Will he sing?

“Maybe,” he replies, deadpan. “There might be a tune or three.”

“It’s so much more labor intensive when you’re filming it than when you’re watching it,” he says of “Glee.” “When you’re watching it, it’s great — there’s all these fast edits and everyone’s singing and dancing and it’s super great fun. But when you’re filming … it’s a lot of work, so my hat’s off to that young cast, because they’re supremely talented.”

As for “This Is Your Mouth,” Neil says he decided to lend his voice to the eight-minute film for a number of reasons: “I have a niece and nephew, and so I like being able to do darker, kind of ‘Harold & Kumar,’ Barney Stinson kind of roles that are a little edgier, but I also like to maintain a presence in the demographic within sort of a more educational slant.”

He adds, “I grew up going to EPCOT Center and things, so I enjoy the ‘narration’ voice.”

Blending pop culture with science and a good dose of humor, “This Is Your Mouth” explores the stickiest, most populated place on earth — the mouth — to show why brushing and flossing alone are not enough to kill bacteria that can lead to broader health problems.

“[The film is] to sort of educate kids, adults, whoever, about not only having nice breath — Listerine style — but also [about] how bacteria is involved in your mouth and how to keep your teeth and gums healthy.”

Waiting for the return of “Glee” over the past few months has been trying, to say the least. Now there’s news about upcoming guest star Neil Patrick Harris that makes us even more anxious for the return of the gang from McKinley High. EW.com reports that NPH will play Bryan Adam, a former glee club member and Will Schuester’s (Matthew Morrison) arch nemesis!

Bryan comes back into Will’s life (in the episode directed by Joss Whedon as a new board member at the school. A source reveals that NPH will tap into his “How I Met Your Mother” womanizing character Barney Stinson a bit, as flashback scenes reveal he was the one that got all the girls and solos, not Will.

Their rivalry grows as Bryan plans to cut the school’s art funding since glee club ruined his expectations of life. As EW explains, “Show choir ruined his life, made him feel he could be a star, but all he could do is book Carnival cruises. Now he wants vengeance.” That vengeance turns into a “climactic duet between Harris and Morrison.” No word on what the song will be, but we can confirm that will be an awful lot of adorable to try and fit on the small screen.

“Glee” returns to FOX on Tuesday, April 13 at 9 p.m. The Neil Patrick Harris episode is slated to air in May.

Jane Lynch vs. Neil Patrick Harris?

Oh, it’s on.

As BroadwayWorld previously reported, Neil Patrick Harris will indeed be appearing on GLEE this season. Entertainment Weekly is reporting that he’ll be playing a former rival of Mr. Schu (Matthew Morrison) who’s come back to town to try to shut down the show choir.

Today, the Entertainment Weekly vis the Ausiello Files has revealed new details of his appearance, stating that “Harris and on-screen rival Matthew Morrison will find themselves up for the same role in a community theater production – hence the “Dream On” duet/showdown [that had been] teased in Ausiello TV.”

In other GLEE news, Cory Monteith and Lea Michele’s voices will also be heard in an episode of “The Simpsons.”

Recent winner of the People’s Choice Award for Best New CDomedy and Golden Globe winner for Best Television Series Comedy or Musical, GLEE, the new musical comedy series, follows an optimistic teacher who – against all odds and a malicious cheerleading coach – attempts to save McKinley High’s Glee Club from obscurity while helping a group of aspiring underdogs realize their true star potential.

The show, which also garnered Golden Globe recognition, stars Dianna Agron, Chris Colfer,  Jane Lynch, Jayma Mays, Kevin McHale.

Due to the success of the first installment of the show, which aired last on December 9, FOX has already ordered a second season of the show and announced that it will soon be launching a nationwide search to cast three new roles, which will be documented on the network in the multi-part special. These newest additions will make their debut on the second season premiere.

GLEE returns to FOX from hiatus on April 13, 2010.

A television staple since his Golden Globe-nominated role in “Doogie Howser, M.D.,” Neil Patrick Harris has since established himself in all mediums. He currently stars on the hit CBS comedy, “How I Met Your Mother”. Named one of the “2008 Entertainers of the Year” by Entertainment Weekly, Harris served as host of the 61st Annual Primetime Emmy Awards and the 63rd Annual Tony Awards.

In the theater, he most recently starred in Arthur Miller’s ALL MY SONS at the Geffen Playhouse. Other recent theater credits include star-turns in the London musical production of Jonathon Larson’s TICK, TICK…BOOM, the Tony Award-winning musical ASSASSINS, CABARET and PROOF.

Additional television credits include the series “Stark Raving Mad,” “Will & Grace,” “NUMB3RS,” the mini-series “Joan of Arc,” both on CBS, and the CBS television movie “The Christmas Blessing.”

Check out the video of his Oscar performance below.

Click here to view the embedded video.

Neil Patrick Harris is one step closer to getting his Glee on. CBS, home of Harris’ regular gig How I Met Your Mother, has signed off on a deal that would have Harris guest starring on the Fox series, Ausiello confirmsWhile nothing has officially been announced yet, it seems inevitable. Back in January, Ausiello reports that Harris and Glee creator Ryan Murphy both wanted to make it happen. With Joss Whedon, who directed Harris in the web musical Dr. Horrible’s Sing-Along Blog, helming an episode, it seems like all the stars have aligned for a reunion.

So as Harris’ guest spot inches closer to becoming a reality, I can’t help thinking about what character he should play. The guest spot is said to include some singing and dancing. The first idea that sprang to mind: Broadway vet sing-off! I’d love to see Harris as a rival to a truly worthy opponent: Matthew Morrison’s Will Schuester. Morrison deserves more than just showing the kids how to white-boy rap. One of my favorite moments of the series so far was when Morrison was matched up with another Broadway vet, Kristin Chenoweth. But their sweet duet was far too brief. How great would it be to see Harris as a blast from Will’s Glee Club past? They can play out their old high school rivalry through a West Side Story-like song and dance number.

What do you think of a Harris vs. Morrison match-up? Is there someone else you’d like Harris to play? Perhaps someone more Horrible? Or do you think he should teach the Glee clubbers about his awesomeness by just playing himself?

Harris, who plays How I Met Your Mother‘s resident womanizer, tweets, “Jennifer Lopez was really great – hot, cool, and funny. And well prepared! She gave me a few pointers.”

Lopez’s character crosses Barney’s path as she stakes on the mission to “break” him after she learns about his gigolo ways from Robin.

“We couldn’t be more excited about Jennifer Lopez joining us on How I Met Your Mother,” executive producer and co-creator Carter Bays said in a statement. “We’re looking forward to a week of revealing outfits and sexy dance moves the likes of which this show hasn’t seen since Regis Philbin guest starred.”

Lopez is also set to guest star on FOX’s Glee, and can be seen in upcoming films such as The Back-up Plan, Double or Nothing and The Governess.

Neil Patrick Harris is hilarious on How I Met Your Mother, but there is another show fans know his talents would shine on — Glee! And apparently we’re close to seeing that wish come true!E! News reports that sources say Neil is very close to closing a deal to appear on an episode of Glee.

Multiple sources say Neil close to signing a deal to appear on the episode Joss Whedon will direct that is said to air in the late spring.

A source who works on the show says, “The plan is for Neil’s acting, singing and dancing talents to all be used… And of course his awesome comedy chops.”

CBS has reportedly not signed off on the deal yet. Although Glee and How I Met Your Mother air on different stations, they are both productions by 20th Century Fox and air at different times.

So, hopefully there won’t be any reason not to let Neil appear on Glee!