Pictures of Tina Fey and Pregnant Jane Krakowski in Costume on the Set of 30 Rock

The writers of 30 Rock have been cleverly concealing Jane Krakowski's growing baby bump all season long, and their latest efforts had her clad in a dog costume for a morning of filming in NYC today with Tina Fey. InStyle cover girl Tina was also rocking a special get-up, with a bright orange trash collector ensemble hiding underneath her long down coat. Both Jane and Tina recently celebrated the milestone of the series reaching their 100th episode, which is a special one-hour event airing on April 21. The extra-long installment is one of the many things we're looking forward to this Spring, and we're also excited for the upcoming release of Tina's book Bossypants.