Make a joke, someone else will finish it.
EX.

Mouse 1: Why did the chicken cross the road?
Mouse 2: MONKEY PANTS!

I'll get us started.
Why did the cat eat the mouse?

The cat just, ate it cause that cat was borreeeedddd <.<
(Who died again??)

Why did your face be a face?

My fae was a fae beCAUSE THE FACE IS A FACE FAIRY CAME AND STOLE MY FACE.

Why did you ross da road?

Because o-- GODDAMMIT ROSS!

What do you call chocolate Lucky Charms in chocolate milk?

DIABEETUS. Couldn't help it...

DIABEETUS

What do you call a potato that doesn't potate?

A toe.

What happened when the frog was trying to get to a wedding?