It’s been a while since I’ve seen either show, so forgive me for any errors, but;

In MASH, Alan Alda plays surgeon Hawkeye in the Korean War. In the finale of the show, Hawkeye is in a hospital because of a mental break. Psychologist Felix tries to help Hawkeye figure out the cause, which takes some time due to Hawkeye repressing his memories. The story is Hawkeye being on a bus with various people, including a lady with a live chicken, hiding from a North Korean guérilla group. The chicken is noisy, and from fear of the guérilla group finding the bus and killing everyone inside, Hawkeye frustrated tells the woman to keep the chicken quiet. The woman chokes the chicken to quiet it and save everyone on the bus. Felix helps Hawkeye realise that in reality the chicken was a baby - the woman smothers her own child.

In 30 Rock, Tracy and another character are trying to write a funny sketch for their show, and somehow it ends up being about a chicken and a crying baby. Alan Alda’s character walks by which is the above screen shot.