ET has your box office scoop!

TINA FEY topped the box office this weekend, as her 'Baby Mama' premiered at No. 1 with $18.3 million, according to preliminary studio estimates.

The culture-clash comedy tells the story of an upper crust single career gal (Fey) who hires a working class surrogate ("SNL" star AMY POEHLER) to carry her child. Tensions rise when the two women end up shacking up for the duration of the pregnancy.

'Harold & Kumar Escape from Guantanamo Bay' debuted in a fairly close second, with $14.7 million. The follow-up to 2004's 'Harold and Kumar Go to White Castle,' brings back stoners Harold (JOHN CHO) and Kumar (KAL PENN) who, this time around, are suspected of being terrorists when their bong is mistaken for a bomb.

JACKIE CHAN and JET LI's 'Forbidden Kingdom' dropped to third with $11.2 million, while JUDD APATOW's 'Forgetting Sarah Marshall' (JASON SEGEL, KRISTEN BELL, MILA KUNIS) fell to fourth with $11 million. JODIE FOSTER and ABIGAIL BRESLIN's 'Nim's Island' stayed strong in fifth with $4.5 million.