My, how they've grown!

As MTV premieres its smash reality docuseries Teen Mom Tuesday with four new moms, revisits the franchise's top 4 most shocking moments from season 1.

Teen Mom took an especially dark turn this summer, when Amber Portwood was taped slapping, punching and kicking her baby Leah's dad, Gary Shirley, on three separate occasions. Five months later, Anderson, Ind., police charged her with two felony counts and one misdemeanor count of domestic violence and battery. If convicted, the reality star faces up to three years in jail and fines of up to $10,000.

Less shocking but still as memorable was Catelynn Lowell and her fiance Tyler Baltierra's June meeting with their biological daughter, Carly, whom they placed for adoption in season 1 of 16 & Pregnant. "I didn't even shed a tear the whole time," Lowell says of the trio's reunion. "I'm not jealous of Carly's adoptive parents. They're amazing."

Revisit these and other must-see moments from Teen Mom in the clip above, ahead of Teen Mom 2's season premiere January 11 at 10 p.m. (EST) on MTV.

Tell Us: What is your favorite Teen Mom moment?

By Allison Corneau for For more Channel Surfing, click here.