From The Hangover [1] to Saturday Night Live [2] to Between Two Ferns [3], Zach Galifianakis [4] has brought us more than a few laugh-out-loud moments over the past few years. Galifianakis turns 45 this week, so to celebrate, we're taking a look at some of the actor's most memorable one-liners, facial expressions, and hilarious dance moves. Who could forget Alan's amazing hair flip, or that time Galifianakis entered a Jennifer Aniston [5] lookalike contest for an SNL skit? Behold, 24 Zach Galifianakis GIFs that are sure to make you crack up.

Source: Warner Bros. [6]

When He Isn't About to Back Down

When He Brags About His Facebook Popularity

When He Did His Best Annie Impression

When He Dropped a Raven Reference

When He Defends His Bag Preferences

When He Got Stared Down by Obama

When He Fully Understands the Definition of Dad

When He Does a Little "Who Let the Dogs Out" Dance

When He Was an Ambidextrous Flute Player

When He Names the Famous Wolf Pack

When He Dances With a Dog

When He Asks the Hard Questions

When He Wore a Wig on Late Night

When He Thinks Caesar Lived in Vegas

When He Really, Really Teases His Hair

When He Attacked Justin Bieber

When He Shows Off the Perfect Hair Flip

When He Tried to Look Like Jennifer Aniston

When He Defends His Croc-Filled Wardrobe

When He Professes His Love For the Jonas Brothers

When He Was Having None of It on SNL

When He Is So Proud of His Pet Purchase

When He Ponders Life's Possibilities

When He Fought With Bradley Cooper