Bibou - arguably Philadelphia's most famous French BYOB - is turning 6 with a couple of substantial changes:

Pierre Calmels is returning to his old kitchen. He has been overseeing BIbou while also running the show at Le Chéri, the polished Rittenhouse Square bistro that he and wife Charlotte opened in November 2013.

Spurring this change: Ron Fougeray, who has been the day-to-day chef at Bibou (and Pierre's righthand man for 12 years - including when he was chef at Le Bec-Fin), is relocating with his family to California. Fougeray's last day at Bibou will be March 29.

Charlotte Calmels says the plan is to shut down Bibou for the month of April for renovations.

When Bibou returns, with Pierre in the kitchen, the menu will become prix-fixe - seven courses for $100 a person.  Charlotte explains that the menu will be more refined. It will still be BYOB and cash only.

Also, dinner will be served Wednesday to Saturday. Bibou's bargain $50 Sunday dinners will go away.

Pierre's move will elevate Steve DeLorean to lead the day-to-day cooking at Le Chéri. DeLorean's resume includes Kraftwork, 10 Arts, and James.

The Voorhees-raised Fougeray's wife, Sarah, is from Orange County, Calif. He said it's long been planned that the couple - and their 2-year-old son - would relocate there. "It's tough," he said of his leaving Bibou. "We put a lot into this."

He expects to find work and eventually open his own restaurant there.