Alan Thicke by Denise Truscello/ WireImage.com
The April 21 episode of How I Met Your Mother is turning into a wonderful '80s flashback. Already marking the return of Robin Sparkles, the outing will feature visits from former teen popstress Tiffany and Growing Pains' Alan Thicke, playing Ms. Sparkles' gal pal and father, respectively, in a newly unearthed video for "Sandcastles in the Sand," a ballad Robin wrote upon being dumped by her backup-dancer beau ( Dawson's Creek's James Van Der Beek).

HIMYM co-creators Carter Bays and Craig Thomas wrote and composed "Sandcastles in the Sand" as the B-side of "Let's Go to the Mall," using iconic '80s breakup ballads such as "Foolish Beat" and "Toy Soldiers" as inspiration.

With Michael Gross ( Family Ties) having guested as Ted's pop and Bob Saget ( Full House) playing narrator, Thicke represents the third classic '80s dad to get involved with the CBS sitcom.

What's your take? Is this shaping up to be one of Mother's best eps? - MWM