The genius that was Amy Ryan's Holly beatboxing on The Office last week got me thinking about other cast additions that have made shows better.

The first that came to mind was actually another Amy Ryan role -- Beadie on season two of The Wire. It took awhile for me to get into the whole dockworkers storyline, but it was Beadie that helped me through.

If a show plans to stay on air for awhile, it needs fresh blood -- but the process of introducing new characters isn't easy (witness how reviled Maya was on Heroes). The best new additions combine great actors with well-written characters.

Here are seven other (fairly recent) new characters that succeeded.