James Patterson's Witch & Wizard series, in the back of each book, features descriptions of books, celebrities, etc. banned by the characters' government, which are all parodies of real-life books and people. There is one parodying Warriors:
THE BRAWLERS: The story of a pack of sentient dogs - some stray, some pets - seeking to fulfull a 'prophecy'.
In the graphic novel of Coraline, there's one panel toward the start where it says "She'd already read all her books", and it shows a stack of books. One is the cover of the first Warriors book, Into the Wild.
In the Pretty Little Liars episode "Run, Ali, Run", Aria remarks; "A's been stalking you for two years like a warrior cat..."
In the The Middle episode "The Math Class", right at the start of the episode, Frankie dumps Brick's backpack out onto the counter. The Darkest Hour can be seen on the top of the pile.