The throwaway panels are indeed the first and fifth based on how the full strip looks. I looked through a few random Sunday Garfield, and it looks like the current format came into existence in 1982. Sunday Garfields now have what Jim Davis calls a "logo box" and a throwaway panel afterwards. So there's either a logo box and seven panels or six panels. I believe Garfield is still formatted like this, and Calvin and Hobbes was until Bill Watterson decided to go for a paneless format on Sundays. Some King Features strips (Beetle Bailey, etc.) have a half-sized logo box and two throwaway panels. (In the 1981 example here, the logo box is also a panel, so that's three throwaway panels. Although they explain why Sarge is opening his drawer in the first place, you don't really need them to understand the strip.)
Originally Posted by nakak
I also find it somewhat interesting that there was a nationally syndicated comic strip encouraging teenagers to become mail carriers.
"If you take away our cartoons, we'll grow up without a sense of humor and be robots."
"Really? What kind of robots?"
-Lisa and Bart Simpson, Itchy and Scratchy and Marge