- "I've killed tougher than you, asshole! Don't get cocky, you're just the appetizer...before I find and slaughter the entree!"
- —-Sweet Tooth
The vehicles are identical except for their color and names; the red one is called Hammerhead and the yellow one is named Slayer. Each has a large, movable bumper on its front, designed to resemble massive fangs. A fin-like row of pipes or smokestacks extends from behind their cabins, prone to emitting smoke and fire.
In combat, the Brothers Grimm rely mainly on their massive bulk, attempting to ram, crush, or trample their opposition. They can raise either set of wheels and slam them into the ground with great force, generating a large, wide-ranging shockwave that damages and trips up enemy vehicles (although the effect is dependent on the target's distance from the shockwave). Both of the monster trucks can also release a barrage of rockets that either home in on Sweet Tooth or fall around him to act as mines.
The greatest asset of the Brothers Grimm is likely each other; they will try to flank Sweet Tooth or have one capitalize on openings the evil clown leaves when battling the other. The numerous buildings can also work to their advantage, as they somewhat limit the movement of Sweet Tooth's vehicle without providing much resistance to The Skulls' titanic trucks. On the other hand, Sweet Tooth can use the larger buildings as temporary cover from the Brothers' missile attacks, and the destructive nature of the battle will likely reduce the cover advantages to near-zero for the monster trucks.
When one of the Brothers Grimm is destroyed, the remaining truck will cover itself in thick metal panels, rendering it immune to all damage. However, the underside of the vehicle remains exposed, prompting Sweet Tooth's gunner to suggest using a C4 explosive charge to destroy the armor plating. To do so, Sweet Tooth must sneak up behind the remaining Grimm (the front is no longer an option due to a pair of low-hanging plates similar to a snow plow) and position himself below it until his gunner can climb onto the undercarriage of the truck. After the Clown minion is on the truck, Sweet Tooth must simply survive against Mr. Grimm's mechanical menace until the C4 is set up and ready to blow.
When the explosives are set, the gunner will request his boss to come and pick him up; however, Sweet Tooth has other plans. Deciding that he wants to see if death by explosion is as satisfying to watch as other, more personal forms of murder, the sadistic serial killer detonates the C4 with the remote left in his car, killing his minion and destroying the Grimm truck's armor. After this, the battle is effectively the same as before, but with one less truck to worry about and with Sweet Tooth unable to use his Specials. Finish off the remaining enemy's health bar to win the battle and complete Sweet Tooth's campaign.
- The front of the armored truck is strikingly similar to Minion from Twisted Metal: Black.
- The Brothers Grimm is a reference to a duo of scholars (known as Jacob Grimm and Wilhelm Grimm) who were the authors of the famous book Grimm's Fairy Tales, featuring fairy tales such as Snow White, Rapunzel, and The Frog Prince.
- No matter which one you destroy first, Mr. Grimm will be in the other one. Even if you destroy Hammerhead first, he will be in Slayer after the explosion.
- This boss marks Hammerhead's first appearance as a boss vehicle in the series.
- It is unlikely that Mr. Grimm actually dies. This is because in Grimm's intro, it shows him riding past the spot where Sophie and Sweet Tooth are buried together, making Sweet Tooth's wish canon in Mr. Grimm's storyline. For Sweet Tooth to get his wish, he must defeat the Brothers Grimm, but since Mr. Grimm is still alive, it means either A: he wasn't present during the battle or B: he escaped before Sweet Tooth could finish him off.