.
Mercury has a moon? Could the Jovian-Plutonian Gravitational Effect give you a floating feeling? Virgin Galactic has bought Pluto and has plans for getting it reinstated as a planet? Nope. All April Fool hoaxes and jokes.

Astronomy April Fools

.
The famous April Fool joke played in 1976 by Patrick Moore resurfaced on the Internet in 2014 as a [supposedly] serious story. Astronomy writer Phil Plait had debunked it earlier in the year, yet was already back again! The story begins, "It has been revealed by the British astronomer Patrick Moore that, on the morning of April 4th 2014, an extraordinary astronomical event will occur."

I like the "it has been revealed by" thing. Sir Patrick died in 2012. I'm sure he was no more likely to return from the grave to spout nonsense than he would have when he was alive. That's apart from the fact that it was not only a joke, but one that made fun of the "Jupiter effect" which was popular in the media in the late 70s. He wanted to make the point that the gravity of distant planets doesn't affect the Earth. Gravitational strength drops off rapidly with distance.

Joke's on me; I forgot it was April Fool's Day.

.
On April 1, 2020, APOD (Astronomy Picture of the Day) asked if this were an asteroid or a potato.

Hmm, sure looks like a potato. And yet - wow! - it also looks a whole lot like the asteroid Arrokoth.

The potato image is by Jack Sutton. The asteroid image was by NASA's New Horizons.

.
Uh oh. Canadian astronaut Commander Chris Hadfield is on the International Space Station and it looks like he means business. Serious business with a grenade in each hand.

But we can breathe easy. This photo was taken on April 1, 2013. And the bottles are actually air grab sample bottles.

Image credit: Canadian Space Agency/Chris Hadfield