Travis' voice was heard in the entire crowd, but he wasn't standing next to the microphone.
When Mr. Hyunh was at the concert, the song started playing before he started strumming.
In "Mr. Hyunh Goes Country," after the scene in the restaurant where everyone wanted Mr. Hyunh's autograph, Mr. Hyunh is seen walking home. He passes a red house where Susie is cheering out the window. Susie lives in the boarding house. However, Mr. Hyunh keeps walking past a green house into the boarding house.
Reference: Scud, the Disposable Assassin
In "Dangerous Lumber," Helga refers to Arnold as "Arnold the assassin," then later calls him "Scud." This may be a reference to the comic book "Scud, the Disposable Assassin."