Continuity mistake: In some of the beginning episodes, whenever George is at work, you can notice that it was originally called "Powers and Sons Aviation", but later in the show it calls them "Powers Bros. Aviation." We even see the Powers Bros. in a few episodes, and in one episode Mel Powers' son smashes up the factory.
Continuity mistake: Max gives Angie a charm bracelet for Valentine's Day with her birthstone, garnet, in it. Garnet is the birthstone for the month of January. Episodes later, George mentions that Angie's birthday was in the summertime because when she was angry with him, there was still light out during dinner.
Continuity mistake: When Ernie is putting in the heat lamp, there is one part when he is holding a piece to it, and reaches up to put it in. In the next shot or two, he has it and puts it in again.
Girl Fight - S2-E15
Continuity mistake: When George goes to meet the counselor, the counselor asks George if he wants a piece of pizza. The piece of pizza the counselor is holding changes after 2 shots. The first two shots show him holding a full piece of pizza with no fold in it. The last shot shows him holding a piece of pizza with a bite in it and it is folded.
Continuity mistake: At Thirsty's, George's brother is drinking a beer with a dark-coloured bottle and red label. It frequently switches from a red label to a green bottle with a yellow label and then back.
Now George Noah's Ex-Zack-ly What Happened (2) - S3-E28
Continuity mistake: The beginning of the episode continues right from the previous episode. George and Angie are wearing the same clothes but in this episode, Angie's hair is suddenly styled differently and she is wearing more make-up.
Continuity mistake: When George comes upstairs to his bedroom, he closes the door carefully behind him. Then he goes to look in the mirror for a moment, and when he heads back to his bed, the door is wide open.
Continuity mistake: When Carmen gets kicked out of Allendel in season 4, George and Angie suggest Saint Teresa's. Carmen says no because it's an all girl school, but she ends up going. In season 5, she says things like "the girls will vote for me, and some of the boys too" (when she was running for class president). She also told Angie about a boy she liked whose locker was right next to hers.
George Helps Ernie See the Cellu-Light - S5-E18
Continuity mistake: Angie is eating chocolate cake before Ernie comes over. Carmen is talking to Angie, and Angie has two big pieces of cake by her fork, but in the next shot, the two pieces are completely gone, and we don't see her put it in her mouth.
Answer: His last appearance was in the episode "God Needles George. He had a tumor in that episode, but in the end was better, and that was the last appearance of him on the show. He was occasionally mentioned afterward, so it is assumed that they still had the dog for the rest of the series.