Damn, I rarely spot Pandaman
But it's cool to find out he appeared quite some times in this episode
Anyways... this was a very good episode. The filler part was actually good, and not annoying. Ace travelling with them until Yuba will be cool and funny
About Black Beard... indeed, like
Vinzer-san said, he was once part of the White Beards, a member of the 2nd Squad, under Portgas D. Ace, the Commander of the 2nd Squad. Now White Beard sent Ace to kill Black Beard since, as Ace implied; he commited the worst crime: killed his "nakama" and abandoned the crew.