WARNING: The following contains spoilers for the DuckTales Season 2 finale, "Moonvasion!"
DuckTales has made a point of referencing classic elements from across the Disney canon. That's extended beyond even the older DuckTales cartoon or Scrooge McDuck comics to include characters and concepts like Darkwing Duck and the Gummi Bears. And the universe is expanding even further in the upcoming third season.
However, the biggest Disney character of all time, Mickey Mouse, made a surprise appearance in the Season 2 finale, albeit in the form of an imaginary best friend for a stranded Donald Duck.
I'm Sorry, Mickey!
Donald Duck has been MIA since the events of "Whatever Happened to Donald Duck?," when the rocket he stole from the Moonites crash-landed on Earth. "Moonvasion!" reveals he ended up stranded on a desert island in the middle of the ocean. Disconnected from the rest of the world for what's revealed to be months, Donald has gone slightly mad. Sporting a massive beard, he's been drinking seawater smoothies and eating sand. He's even created his own Wilson, a la Castaway, to keep himself busy. However, instead pg a volleyball with a crudely painted face, Donald has constructed a best friend out of melons: a large melon carved with a big smile and two eyes, with two smaller melons as ears.
Essentially, Donald's Wilson is a pastiche of Mickey Mouse. To drive home the point, Donald gives the melon a squeaky voice that's exactly in character with Mickey. Everyone is disconcerted by this development, but they all roll with it until Della, in a moment of frustration, accidentally kicks the melon into the ocean. However, that actually saves everyone in the end. Donald and Della's cousins, Featherly and Gladstone, are moving through the ocean when they spot the melon floating by. Picking it up, they notice the island where the rest of their family is stranded. That allows them to rescue the others, and bring them back to Duckburg to help save the world.
DuckTales has introduced a number of characters from across other Disney properties. However, the entertainment giant has reportedly always been wary of allowing their flagship character, Mickey, to appear on the series. Co-Producer/Story Editor Frank Angoes has addressed his efforts to bring the icon to Duckburg, writing, "[Mickey's] way above my pay grade. I had one story that involved him and one that mentioned him, but both were vetoed."
That's part of what makes Mickey's appearance as a melon all the more hilarious. Despite it obviously being Mickey Mouse, it's technically not the character. Despite the distinctive ears and voice (provided by current Mickey Mouse actor Chris Diamantopoulos, who also plays Darkwing Duck on DuckTales), the melon is clearly intended as a joke reference. The voice is even listed in the credits as simply "Melon." It gives the producers a chance to have more fun with the character than they would have otherwise. When Melon kicked away over the ocean, he yells, "See you real soon!" as Mickey did at the end of each episode of Mickey Mouse Clubhouse. They technically get to kill Mickey by having Gladstone Gander eat the melon in front of an incredulous Donald, imbuing the subplot with a darkly comic edge.
If DuckTales isn't allowed to actually use Mickey Mouse, this is the next best thing. But with other Disney characters like Goofy set to make their DuckTales debut in the upcoming third season, there's always a chance the real deal could crop up. It'll be up to Donald to explain the melon tribute, though.