Monica Geller: Phoebe? Do you have a plan?

Phoebe Buffay: I don’t even have a “pla.”

From Friends – Season 1 Episode 4: ‘The One with George Stephanopoulos’ (1×04)

Quote Meaning
Rachel, Monica and Phoebe are talking about their futures. What their plans for the future are and how all things are gonna come together. But Rachel questions the part about everything coming together putting Monica and Phoebe into bit of a depression as they don’t know what the future will bring and do they even have a plan for it. Monica says she doesn’t have a plan and asks Phoebe if she has one. That is where she says the famous line “I don’t even have a pla.” She makes a bit of a play on the words, trying to one up Monica, that she not only doesn’t have a “plan”, but emphasizes the word by leaving out the last letter – not even have a “pla”. She could also mean she never even thought about any plans, so the word is non-existent for her.