Like many others have said already, this was fail.
It had the chance to be a hilarious episode, but somehow, the staff managed to botch this one so much that only the instant when Pikachu and Piplup threw themselves at each other for the first time was funny - and that instant lasted about ten seconds.
Firstly, Shimura's seriously starting to slack off again with most characters - especially the main trio - looking extremely sloppily-drawn.
What was far worse, though, was the terribly lame script.
The group's reaction to the sudden attraction between Pikachu and Piplup wasn't even remotely amusing. Potential exaggerated, anime-style expressions of gobsmacked-ness had to clear the way for the ever-so-redundant, standard reactions of surprise, slight shock and worry. Wow, hilarious. Pikachu and Piplup could've collapsed with a fever and it wouldn't have made a difference.
It didn't get any better when Professor Kodama turned out to be a boring-as-cardboard researcher with little spark. I don't care how many people are annoyed with the crazy professor stereotype - it would've certainly fit in better than another personification of "I-had-good-intentions-but-it-didn't-work-out-the-way-it-was-supposed-to" that would ultimately be met with understanding from everyone.
Also, everything reeked of wasted opportunities to spice up the craziness even more. Buizel somehow getting involved and throwing itself at Pikachu as well, creating an awkward triangle; war ensues. Buneary appearing and being mortified at the indecent display of a not-so-endearing Pikachu.
The entire story had too much analytics and too little WTF. If they want to do a fun plot of this caliber, they can't just rely on a single core idea carrying the entire episode by itself and continually getting laughs. It needs chaos and chain reactions of funny occurrences - it almost seemed to me as if they were afraid of not making sense in the end, but isn't that a pretty trivial thing to worry about in a crackpot story?
Anyway, as a result, everything and everyone in this episode was way too matter-of-fact and insistent on giving explanations. Who on earth cares about the why? This is crack. Crack doesn't need justifications. Crack should plow its way through the plot with its buddies, screwball comedy and meaningless hurly-burly, without giving a damn about boring things like reason.