Orbot

SA-55, commonly referred to as "Ergo" by fans, is a small robotic assistant of Dr. Eggman, appearing in cutscenes during Sonic Unleashed.

The diminutive droid is a fixture of Eggman's control consoles for most of the game, relaying information to the Doctor and making sure the processes of his plans are carried out correctly. When inactive, he folds up into a sphere, and pops back up whenever Eggman needs someone to yell orders at. Although he is always obeys the Doctor's commands, SA-55 is utterly, comicly tactless in criticizing his master when Eggman's plans go awry, and even laughs openly when the scientist takes a rock to the skull in Mazuri. SA-55's cynical opprobrium frequently proves annoying to the Doctor, prompting him to make flustered defences about how "Taking over the world is... err... no fun if it's too easy!". In the final cutscene beside the wrecked Egg-O-Matic, as the robot lists all the ways in which the scientist's plans have once again failed miserably, Eggman finally snaps and chases SA-55 off into the sunrise.

Trivia

• The robot's actual name, SA-55, does not appear anywhere within Sonic Unleashed itself; fans gave him the name "Ergo" on account of his propensity to use the word frequently while dissecting (and rubbishing) Eggman's plans.
• SA-55's real name was eventually revealed on the BumbleKing forums by Ian Flynn (head writer of the Archie Sonic the Hedgehog comic), who found the name in the script of Sonic Unleashed.
• SA-55 is l33t-speak for "sass", an accurate description of the robot's personality.
• According to an interview with Mike Pollock, SA-55 is voiced by Chris Collet, the voice director of Sonic Unleashed, who also voices some humans in the cutscenes.