A R.O.B. Sentry (ロボットアタッカー Robottoatakkā, Robot Attacker) is a member of the R.O.B. Squad and an enemy in the Subspace Emissary mode, encountered only on the Isle of the Ancients. It has a similar appearance to the hidden character, R.O.B.. The R.O.B. Sentry replaces Primids on the floating island, attacking with melee moves (hitting opponents with their arm in a fashion similar to R.O.B.'s forward tilt). Also, they too have variations that attack in different manners, as Primids do. According to the trophy description for R.O.B. Blasters, R.O.B. Sentries are equipped with beam firing capabilities, although they choose to participate in hand-to-hand combat.
 Role in Subspace Emissary
In addition to defending the Research Facility and the Subspace Bomb Factory, the R.O.B. Sentries served a vital role in Tabuu's plot. Whenever the Ancient Minister dropped one of the Subspace Bombs, two R.O.B. Sentries were required to arm it, being sacrificed in the subsequent explosion. The R.O.B. Squad was initially under the command of the Ancient Minister, but during an attack on the Subspace Bomb Factory, Ganondorf took control of them, forcing them to even attack the Ancient Minister. This cut scene is the only time R.O.B. Sentries can be seen using their beam firing ability.
 Damage taken
 Trophy Info
A robot with a two-armed shot. This R.O.B. uses the booster on its base to propel its jumps. Often used in the Subspace Army bomb factory in defense or labor roles, the R.O.B. Sentry also works as a detonator. Its emotional capacity is unknown, but it has utter trust in the Ancient Minister and obeys him unwaveringly. This production model has been made in great numbers.