Nathan Fillion is an Emmy-award winning actor par excellence, and he created this highly popular original phrase. "Bam, said the lady", along with its short form, "BSTL", is used as a primarily positive interjection to support prior statements. Here is its meaning as he describes it on his NathanFillion on Twitter page:
"Bam, said the lady" means:
•There you go.
•Done. And... scene.
•Look at that!
Nathan Fillion, the gorgeous, sexy, and supremely talented leading man who stars in the fabulous TV series "Castle", also says his phrase on the show!
(BSTL can be used in place of "Bam, said the lady.")
Nathan Fillion: "That's right. There's this kind of stuff going on in LA. Eat your heart out, NY! Bam, said the lady. "
Nathan Fillion: "Have to work Saturday and Sunday. Birds go hungry. Bam said the lady."
Nathan Fillion: "Just did a Feed the Birds in episode three of Castle. Also, tried to squeeze in obscure Firefly reference. Bam, said the lady."
Nathan Fillion, after completing filming of an episode of Castle: "Episode 4. Scene 34. Bam, said the lady."
Query: "What's a good catch phrase?"
Nathan Fillion: "Mine: Bam, said the lady!"
Nathan Fillion: "The Incredibles was the best movie ever made. Ever. Made. BSTL." (Bam, said the lady.)
Nathan Fillion query: "Anybody else putting BAM, SAID THE LADY into their daily vernacular?"
Nathan Fillion's faithful followers' answer: "Oh, yeah! Bam, said the lady!"