They say that marriage is “the biggest club in the world,” but if that’s the case, then becoming a Dad comes in at a reasonable second.

In 2012, many celebs became fathers — some, like Chris Hemsworth, for the first time, others, such as Ben Affleck, who are already expert hands around the diaper bin.

In today’s Celebuzz gallery, we salute the Hollywood men who gave away (some) of their nightlife (or sleeping) hours this year in exchange for warming bottles and administering ear medication.

Some of Hollywood’s newest members to the dad club will need to dust off their copies of Babies for Dummies, including Bruce Willis, who hasn’t had a new baby to cuddle since welcoming daughter Tallulah with his then-wife Demi Moore 17 years ago.

Who do you think is the sexiest new Dad of 2012?  Enjoy the galleryof Hollywood’s hottest dads — then share your favorite in the comments below.

He’s all that.

Freddie Prinze Jr. was spotted taking his 3-year-old daughter Charlotte to school in Los Angeles on Thursday. The dutiful dad carried both Charlotte and her pink backpack as they walked to school. This is the first time Prinze Jr., 36, has been spotted out since becoming a second-time dad.

The former film star and his wife Sarah Michelle Gellar, 35, welcomed a son, on Sept. 24. The pair have been married since 2002.

How does this Hollywood couple make it work? 

Gellar, who returned to TV last year in the ill-fated Ringer, told Us Weekly back in February her husband loves being a stay-at-home dad.

“He loves it. We fight over who gets to stay home,” Gellar said. “You’d think it would be the opposite, that the parents would be like, ‘No, I’ll go to work!’ but he’s like, ‘You stayed home for two years! It’s my turn!’”

“He and Charlotte have too much fun,” Gellar added. “I’m jealous!”

The happy couple first met while making the 1997 horror flick I Know What You Did Last Summer.

Freddie Prinze, Jr. isn’t the only hot celebrity dad in Tinseltown. Click through the gallery, above, for more doting fathers and their little ones.