Dynamo made its first appearence in Uh Oh Dynamo. After the girls defeated an incredibly strong monster, the Professor's over protective parenting skills kick in. As a result, he created Dynamo to help the girls defeat the monster. Though the girls were reluctant to use it, the eventually did so when faced with that same monster's larger relative. Though the monster was defeated, the Dynamo itself did extensive damage to the city, leading the Mayor to demand they never use it again. Despite this, the Professor didn't dismantle it, possibly out of setiment, though as shown in Oops, I Did It Again, his memory of it is not that fond.
The second appearence of the Dynamo is in Live and Let Dynamo, where it is intentionally causing the destruction of the city. As the girls fought the machine, they wondered who could possibly be in it, ruling out villain after villain as to who the pilot could be. In an ironic twist, the Dynamo's pilot was revealed to be the Mayor, totally unaware of how to use the machine. In The Powerpuff Girls Crossover, it was used by General Grievous.