I'm torn as a Garfield fan. I like Jon's pestering calls to Ellen. I like Jon's perpetual ultimate-crush on Dr. Liz Wilson. I guess I'm a Liz-Jon shipper at heart. It's a stroke of storytelling genius that Garfield is wrapped up in the relationship, a sort of love/desperation/indifference/whatever triangle. Though the endless thirty-second chats with Ellen have the tang of high concept, I appreciate that the gimmick helps keep the Garfield cast down to a bare minimum of players.
The one-sided phone conversation is a tricky tightrope to walk for the dialogue writer. It's tough to avoid the obvious cheats wherein a character repeats what someone says as a confirming question. Today's strip is guilty as charged, but I'm letting it off the hook for the why-even-bother? total failure of exposition opening line "What's that you say, Ellen?"
As for the punchline (some days even I'm not sure why Garfield delivers some lines to Jon, some lines to the Keepers of the Fourth Wall), the "dark cloud" is obviously Ellen's amnesia. But does Garfield believe the "silver lining" is for Jon, who now has a fresh shot at traumatizing Ellen? Or is the silver lining for Ellen, Garfield grinning as he lives vicariously through the brain-damaged woman, envying a life in which he does not remember Jon.