CREATE TABLE table_20421 ("Episode Number" FLOAT, "Air Date" TEXT, "Guest Host" TEXT, "Musical Guest  ( Song performed ) " TEXT, "Who knows the most about the guest host? panelists" TEXT)

List the date when Jeremy Edwards and Grace Adams-Short were the panelists.
SELECT "Air Date" FROM table_20421 WHERE "Who knows the most about the guest host? panelists" = 'Jeremy Edwards and Grace Adams-Short'
SELECT "Air Date" FROM "table_20421" WHERE "Who knows the most about the guest host? panelists" = 'Jeremy Edwards and Grace Adams-Short'