- Planet Earth is featured in this card's artwork.
- "Terra Firma" is Latin for "Firm/Solid Ground".
- This card is very similar to Elemental Hero Neos in ATK and DEF, appearance, and their ability to use other monsters to become stronger. Also, they represent almost opposite things to humans, Terra Firma representing Earth, and Neos representing Space.
- Terra Firma's attack is equal to the combined attack of its fusion materials.
- This card is one of the "Legendary Planets". "Big Saturn", "Splendid Venus", "The Tyrant Neptune" and "The Despair Uranus" are also members of this group.
- This card is the first Planet monster to appear in the manga.
- This is the only Planet card to not have its name exclusively in English alphabet characters and punctuation.
- This is the only Planet card to have its name deviate from the standard naming pattern (in the OCG: "The (word) Planet's name in all caps", whereas the TCG equivalent is simply: "(same word as the OCG) Planet's name") following that pattern, this card would be named "The E-Hero EARTH" in the OCG and "Elemental Hero Earth" in the TCG.
- So far, this is the only Planet card that is a Fusion monster, while the others are Effect Monsters. Also, this is the only Planet card that belongs to another Archetype besides Planet Series.
- This card bears a resemblance with a character from Dragon Ball Z, Frieza in his final form because of the white skins and the purple/blue sections on their heads and shoulders.
- This card bears some resemblance with Colossal Fighter.
- This card's color scheme bears resemblance with the Duel Academy Duel Disk.
- This is the signature card to Jaden Yuki in the manga while in the anime it's Elemental Hero Neos.