Not to be outdone by Google, Twitter welcomed Lady Gaga to their SoMa offices this afternoon to talk with co-founder Evan Williams (@ev).

"Just interviewed @Ladygaga at Twitter HQ. What a trip. Lovely, smart, and articulate," Williams reports.

And, what with Twitter HQ just one block away from SFist HQ, your editor shamelessly ran over to Folsom and Fourth only to see Gaga's tour bus pull away. Exciting stuff, folks.

Thanks goes out to Troy Holden for snapping this shot of Gaga!