From the Super Mario Wiki
Mecha-Chomps are mechanical Chain Chomps that Mario and Luigi encountered during the events of Mario & Luigi: Superstar Saga. However, instead of being restricted by chains, Mecha-Chomps have dog-like bodies, and move around on wheels.
They are found in Woohoo Hooniversity, but never appear on the field, instead showing up in battle alongside Laser Snifits and Viruses. When attacking, the LED on the Mecha-Chomp's face cycles through red and green, eventually stopping on one of the two. The Mecha-Chomp then throws its head at the appropriate target – Mario if it is red, Luigi if it is green.
Once the Mecha-Chomp has been damaged, it starts to malfunction. When malfunctioning, a Mecha-Chomp reverses its targets – red for Luigi, green for Mario. Additionally, the item it drops changes while malfunctioning.
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