Answer 1

Deerling's form changes according to the current season.
lf you caught a Deerling in Winter, and took it out during the Summer, it would change into its Summer form.

The same thing for its evolution, Sawsbuck.

• Spring: January, May or September
• Summer: February, June or October
• Autumn: March, July or November
• Winter: April, August or December

Comments

A small addition: it doesn't change immediately when you take it out of the PC, you need to put it in your party, save then reload the game.

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Ohh, l was not aware of that.