Minami Takayama voiced herself apart from Conan in that episode. Although the joke isn't easy to get if you don't know about seiyuus and J-Pop, many foreign dubs made the actress voicing Conan also voice Takayama.
The Danza: Police inspector Wataru Takagi is exactly named for his voice actor, as his character was created out of the anime. Likewise, Inspector Chiba takes his voice actor's last name, and Tooru Amuro is voiced by Tōru Furuya. Amuro's situation is unique, however, as he is the only character of the three that was introduced in the manga first.
Throw It In: Takagi was supposed to be an unnamed extra in the anime, but while ad-libbing some lines Chafurin as Megure asked "Hey, what's your name?". Wataru Takagi filled in by saying "It's Takagi, sir!", and there came his name.
Hey, It's That Voice!: Um...everyone? Seriously the show has so many single episode focus characters and has been running so long, that literally every Japanese voice actor has been on it at some point.
You can also hear several familiar voices in the dub.
It is interesting to note that a significant number of voice actors that voiced recurring characters in Detective Conan had voiced important characters in Legend of Galactic Heroes before:
Of special mention is The Kidnapping of a Popular Artist Case (episodes 81-82), where the Victim of the Week is Minami Takayama, the lead vocalist of Two-MIX who also happened to be the voice actress of Conan. The Celebrity Paradox is immediately lampshaded when the cast noted how similar their voices are.