Mayim Bialik and Joey Lawrence

Old Navy has a new chief floral officer on board and she definitely knows a thing or two about flower power.

Blossom star Mayim Bialik — rocking a signature big hat, natch — stars in a new ad for the clothing company's latest spring dress offerings. In the spot, Bialik gets a surprise visit from her on-screen little brother Joey — excuse us, Joe — Lawrence, who pops up as a gardener to spout his famous line from the long-running NBC comedy. (For those who don't know, it starts with an "W" and ends with a "hoa!")

These days, Bialik can be seen on The Big Bang Theory, while Lawrence stars on the ABC Family sitcom Melissa & Joey.

Get your dose of '90s nostalgia here: