A couple surprises.

The verdict is in and Ditto is guilty of disguising itself as these Pokemon in the 2020 Pokemon Trading Card Game Sword & Shield GO series:

Cards Ditto is Disguised As
Market Value*
Common Reverse Holo 006/078 Spinarak $5.19
Common Reverse Holo 013/078 Numel $4.92
Common Reverse Holo 059/078 Bidoof $6.12

It was originally believed that Ditto only disguises itself as Bidoof.  You can tell if the card can be peeled to reveal a Rare Holo 053/078 Ditto if there's a Ditto graphic on the bottom left of the card.

Interestingly, a Rare Holo 053/078 Ditto has been selling for $6.33.* Why not purchase the cheapest unpeeled version of the card and peel it yourself?

*The market value is the average price of what these cards are selling for as of this writing on TCG Player. This does not represent the cards future value.