He was the voice actor for Balloon until "The Stacker", where he was fired after deleting episodes from AnimationEpic. He returned to voice Balloon in "Breaking The Ice", but was replaced by Ben Cross in "Let 'Er R.I.P."
In mid-September 2011, Nate Groth, hacked into AnimationEpic's channel and deleted the current episodes at the time, which were the original 1 through 5.5 (along with various other II-related videos - "The Taco Show", "Nickel's Tips On Conserving Water", etc.). Due to this, Groth was fired and his lines were re-used frequently for Balloon throughout the first season.
Fans and contestants show major dislikes towards Balloon for this. Adam, the creator of the show, confirmed that Balloon's elimination in Inanimate Insanity was mostly because of the hacking.
However, according to the credits in "Breaking The Ice", the original voice actor was rehired and provides Balloon with new lines, which the character even recognizes. Groth continued to voice Balloon until "Let 'Er R.I.P.", where Balloon's voice was permanently replaced with Ben Cross'.