Well, clearly Ivy and Sherlock need to have more CR because she may not necessarily be smarter than him, but she certainly knows more than him.

Also, Amy and the Eleventh Doctor have a detective agency. Operating out of a hat store. Sherlock could stop by and mock them. The Doctor at least is at least as smart as Sherlock? And Amy will just flirt with him or... be annoyed and sassy, whichever.