Ex presidents tend to stick to an unwritten gentlemen's agreement to sort of step aside after their terms are done, write books, give speeches or whatever, and let the new guy run things without getting involved.
President Donald Trump has proved to be a commander in chief like no other in recent memory, though, and his predecessors Presidents Jimmy Carter and Bill Clinton are piping up in rather unprecedented fashion.
They're totally trolling Trump on Twitter.
President Carter rolled out some facts without commentary, although it's hard to miss the intended message:
Clinton is taking a different approach, dragging Trump with humor. Posing with a giant insect statue he tweeted a "breaking news" bulletin that the Clinton Presidential Center had been "bugged."
It'd be hard to see that as anything but a ding at Trump's never-proved allegation that the Obama administration "wiretapped" him during the presidential campaign .
President George W. Bush has been less pointed but has voiced perspectives on foreign affairs policy that differ from Trump's:
And President George HW Bush has been under the weather. He posted this nice photo with no mention of politics - just family: