Notes:

Betty uses Evergreen's Crown to wish for the power to protect Simon.

She merges with GOLB, and disappears from Ooo seemingly forever.

Simon is seen in the Time Room; aparrently failing to bring Betty back, like how he couldn't bring Margles back for Magic Man in "You Forgot Your Floaties".

He probably moves on in his life seeing as it's shown later that he hangs out with Bubblegum, Marceline, The Ice Thing and Turtle Princess.