Spears and Chalke will appear in the episode slated to air March 24.
"Continuing his passionate quest to find the woman who will one day be his wife, Ted (played by Josh Radnor) pursues his beautiful dermatologist, Stella. While Stella turns down his repeated efforts for a date, her office receptionist, Abby, becomes smitten with Ted," a press release announcing the installment said.
"Scrubs" star Chalke will play the dermatologist, while Spears has been cast as the receptionist.
Abigail Breslin wears sheer paneled gown for 'August: Osage County' premiere
Rare Chinese turtles hatch at New York City zoo [VIDEO]