While Ash and friends are still discovering new islands, they come upon the seven Grapefruit Islands where groves of giant grapefruit are ripe and in season. When it looks like thieves are stealing the grapefruit, Ash, Tracey and Misty volunteer to help catch them. Surprisingly enough, what looked like hundreds of thieves was actually just one giant, hungry... and sleepy culprit!
Ash says that Snorlax was doing the "blubberfly" while swimming, a play on the butterfly swimming stroke and also a reference to a non-Pokemon species. The closest Pokemon analogy to a butterfly would be Butterfree, which also appears in this episode.
The "Who's that Pokémon?" in this episode is Ivysaur.