I just want to confirm that I'm interpreting this correctly.

So DP20-002 Plastic Man's IT WAS ME THE WHOLE TIME! Trait states: "FREE: Choose a friendly Disguised Plastic Man object on the map and place it into a square adjacent to its current square". However, the Mailbox has Immobile, so am I interpreting correctly that, despite what his Trait says, you cannot do the FREE placement with the Mailbox??

If so, then .

That's a silly, goofy problem to have.

In other words, it is typical WizKids.