Billy Gibbons of ZZTop celebrated his birthday on December 16th. That same week, he appeared in the Christmas episode of 'Bones' as Angela's father ("The Man In The Fall-Out Shelter"). He's credited at the IMDb.com as "Angela's Dad", so we don't know what his character's name actually is.
Dialogue doesn't help, because we weren't privy to it. Everybody at the Jeffersonian Institute had been quarantined by a possible viral contamination, so all of their holiday visitors had to stay behind the Plexiglas to "be" with their loved ones. And each visit was seen but not heard in a montage overlaid with music (the current pet peeve for so many televisiologists).
But we were given a rather strange clue as to his identity by Angela when she said that her Dad was famous, but please don't make a fuss over him.
As his own self, Billy Gibbons is certainly recognizable, even to those who aren't really familiar with ZZTop. (Although it wouldn't be unbelievable if "Tempe" Brennan didn't have a clue to what ZZTop means.) If he was that famous that Angela had to warn her jaded coworkers not to make a fuss over him, then couldn't it be possible that he was appearing as himself?
One argument against that might be that Angela's last name is Montenegro.
So? Jennifer Jason Leigh's father was Vic Morrow. They don't share the same name.
Couldn't it be that Angela was the result of one incredible hot night with a ZZTop groupie of Asian background? (The actress, Michaela Conlin, is of Chinese/Irish heritage; but if she was like me, she'd just name the state where she grew up whenever asked where her people came from. I just tell those nosy bastids "Connecticut - that's as far back as I take it.")
And this Billy Gibbons of TV Land did the right thing - so far as he could - by making sure he took an active enough role in her upbringing.
The reason I include the League of Themselves as actual TV characters is because those real-life celebrities have been fictionalized to fit the story. In the Trueniverse, Art Linkletter was never trapped on a disabled flight with a little girl robot; Tim Russert is not related to a Baltimore homicide detective; and Sammy Davis, Jr. never planted a big wet one on Archie Bunker while visiting his home in Queens. But those scenarios were seen on 'Small Wonder', 'Homicide: Life On The Street', and 'All In The Family', respectively.
This past season we had a major case of fiction when it came to the show 'Curb Your Enthusiasm' - for Larry David spent the entire year dithering over whether or not he should donate a kidney to real-life comedian Richard Lewis.
By the final episode Larry even died and went to Heaven. (Of course, he didn't stay there long, but that's because the spiritual Host can control who they hang out with. It is, after all, Heaven.)
It's not like real-life celebrities haven't done the Toob-Steak Boogie with Toobworld characters in the past. Ellen DeGeneres had a one-night stand with the host of 'The Larry Sanders Show', and you can ask Vince Chase's 'Entourage' all about his relationship with Mandy Moore.
And even though we never saw it happen, who's to say Mae West didn't play a little "Catherine The Great" with 'Mr. Ed' during the commercial breaks when she was a guest star?
I know. Ewwwwwww.
So until such time as a future episode clears this up, I'm going to stick with the assumption that Angela Montenegro is the daughter of the televersion of ZZTop member Billy Gibbons, born outside of marriage.
I'm not sure if this means that 'Bones' can now be linked - for the time being - to Ellen DeGeneres' sitcom 'Ellen'. ZZTop performed in the episode "The Pregnancy Test" on November 20th, 1996. But that was during the opening title sequence which was always outside the insular world of the rest of the episode. In fact, when Ellen appears in those sequences as well, it's o'bvious she's doing so as Ellen DeGeneres and not as Ellen Morgan.
So maybe ZZTop appeared not as their human selves, but as that ghostly trio in their music videos......