They indeed had a new episode on at 6:30pm PST.
It was one (the standard 30 minute program) containing the following two episodes:
Shuffle-Boarding
Slide Whistle Stooges
The first one was a Mermaid Man & Barnacle Boy-themed episode, and the second one had to do with slide whistles - even Squidward was all "happy & smiley" around SpongeBob and Patrick during much of this episode.