If You're a Monster and You Know It

"If You're Happy and You Know It" is a great song for adapting to different storytime themes, and it's a great way to get kids on their feet and moving around due to the different actions you can pair with the words. I use this version with monster and spooky themed books.

I found this on The Storytime Source Page, located here.

Lyrics
If you're a monster and you know it, show your claws

If you're a monster and you know it, show your claws

If you're a monster and you know it

Then your claws will surely show it

If you're a monster and you know it, show your claws.

Repeat with:  

Grind your teeth,

Stomp your feet,

Growl out loud