Why does my cat wait in front of the bathroom door when I go inside the bathroom and close the door?

Silly. Your cat assumes every room in the house is theirs. When you close a door, they are like, "WTF?!" That's the same reason they sail into the closet the instant you open the door.

Your cat is your shadow. He/she will go where you go. I find it endearing.

Cats don't understand doors!

All cats and dogs like to go into the bathroom with you. Toddlers do, too, but not for the same exact reasons. If you close the door, your cat will wait there for you, and might even go in there after you leave. I suspect it is a scent marking thing with the animals.

Because you're being rude and didn't leave the door open so it could watch.

Cats life essence is derived from making us uncomfortable. You're stifling kitty's lifeforce...

Open the Door!
The cat 🐈 just wants to sit in the Big Box 🛁 and check for spiders!

[c=#003BB2]The cat wanna make sure that you return n not leaving him her alone...[/c]

Leave the door open.

She/He wants in.

It would doubtless join you if you didn’t close the door. Protectiveness, or curiosity. 😸