H.E.L.P.eR. stands for "Humanoid Electric Lab Partner Robot." It's discussed during the audio commentary on the episode "Tag Sale, You're It" that Jackson Publick originally voiced the sounds for H.E.L.P.eR. Then Doc Hammer ran this through Soul-bot, a robot that they have at Astrobase Go! to give us H.E.L.P.eR. sounds. You can see Soul-bot at the end of every episode in the Astrobase Go! i.d. It was also discussed that they gave up making new sounds after a while and just use the same ones over and over.
Brock Samson's devotion to Led Zeppelin surfaces in several episodes. Some references are subtle - when driving the Charger, Brock almost always is listening to facsimile Led Zeppelin songs - while others are more overt, such as Hank rifling through Brock's collection of "Zep" cassette tapes, or Brock drawing the logo of the band's label instead of completing the essay portion of a written exam. He even has a (currently incomplete) tattoo of the label on his arm.