CodePen OEmbed Wordpress Plugin - Rating, Reviews, Demo & Download
Plugin Description
Add CodePen to the available oEmbed providers
If you’re blogging in Markdown via the WP-Markdown plugin, oEmbed doesn’t work, but Jetpack now enabled Markdown blogging and it does work through that.
oEmbed only works through post/page content in WordPress, but you can bring it to comments as well:
You can read more about it here for additional information