You just know that Regis Philbin would never find himself in this kind of mess -- mainly because he probably doesn't know what a tranny is.

Neil Patrick Harris found himself in apology mode Friday, after catching flak for using the phrase tranny on Thursday's Live! With Kelly.

Truly sorry for saying the word 'tranny' on Live this week. Twice! Harris wrote on his Twitter account. Should have been more thoughtful. Didn't at all mean to offend.

Harris' gaffe came during his guest-hosting stint, during a segment with Science Bob, who introduced Harris and Kelly Ripa to the joys of sulfur hexafluoride, referred to as helium's evil twin by the visiting science expert.

Taking a huff and marveling at the voice-deepening properties of the substance, Harris busted out a Darth Vader impression. Then, recognizing how much he sounded like the Silence of the Lambs character Buffalo Bill, he intoned, Put the lotion in the basket!

As his voice returned to normal, Harris cracked, I've never sounded more like a tranny in my life. (Presumably, Harris was referring to Buffalo Bill, not Darth Vader.)

The Gay and Lesbian Alliance Against Defamation lauded Harris's mea culpa, noting, It's heartening to see a celebrity of Harris' stature recognize and apologize for using the slur in such a timely manner, and for greater media attention being paid to its use. Many people do not realize that the word tr*nny is one of the most hurtful and dehumanizing slurs that transgender people hear. Most transgender people associate that word with personal experiences of violence, hatred and derision.