Anypony

A play on the phrase "anyone", where "one" is replaced with "pony". It is used by the characters in My Little Pony and is also commonly used by bronies.

is anypony there?

Somepony

A play on the phrase "someone", where "one" is replaced with "pony". Used by the characters in My Little Pony and is also commonly used by bronies.

Has somepony seen the new episode of MLP?

Nopony

A play on the phrase "no one", where "one" is replaced with "pony". It is used by the characters in my Little Pony and is also commonly used by bronies.

Nopony saw him last night.