What about the "Sign in to iCloud" one?

Phone: I know you probably opened your phone for a reason, but would you mind signing in to iCloud? [OK] [Maybe Later]

Me: Maybe Later.

Phone: Ok, but would you mind signing in to iCloud? [OK] [Maybe Later]

Me: Maybe Later.

Phone: Ok, but would you mind signing in to iCloud? [OK] [Maybe Later]

... repeat infintely until...

Me: Ok. [Then find the little arrow in the top left corner to get back to phoning].

Extra points for immediately locking my AppleID every time I finally break down and type my password in, forcing an email => browser "unlock your appleID" journey.

Some days I go through this whole experience four times in a row before it finally settles down. Then I make the classic blunder of opening one of my iPads and the whole thing starts again on both devices.

I assume it's just their form of blackmail to force me to upgrade to their 2FA thing so that they can finally lock me out of my old devices for good.