We're having an incredibly hard time believing that tomorrow is Justin Bieber's 20th birthday! It feels like just yesterday he was 15 years old and releasing his very first EP My World. Where did the time go?!

Since today is the very last day of Justin's teens, we've decided to take a look back at his younger years — you know, before he hit his growth spurt and turned from adorable to hot seemingly overnight.

Click through to see hilarious photos of a much tinier Justin hanging out with stars who were way taller than him, then let us know which photos make you laugh the most in the comments below. Can you believe Justin will be 20 tomorrow?!