https://thetruesize.com/ is also fun.

Just use the search to add Antarctica and another region (like say Australia, or North America), then drag them to the equator to compare their sizes.

Changelings (d&d style), Doppelgangers, Werewolves, really any kind of shapeshifter, the more shapes/types they can take on the better.

My list for Firefox:

• Always on Top
• Display #Anchors
• Firefox Multi-Account Containers
• Regex Search
• Simple Tab Groups
• Stylus
• uBlock Origin