Joey's children -- Jerry, Lewis, Phyllis, and Joan -- are named after legendary Vegas entertainers Jerry Lewis, Phyllis Diller, and Joan Rivers. Joey and the rest of the Gladstone family come from Las Vegas.
In season 1, Joey said he was single now he has four children. Jerry, Lewis, Phyllis, and Joan are Ginger's children meaning they are Joey's adopted children.
Bob Saget (Danny), Laura Bell Bundy (Ginger), and Virginia Williams (CJ) have all appeared in How I Met Your Mother throughout the series.
Laura Bell Bundy (Ginger) and Bob Saget (Danny) both appeared on How I Met Your Mother at the same time, as "Becky" and narrator "Older Ted".
In this episode, Danny tells D.J. that he's 60. This is accurate to Bob Saget's actual age since he was born in 1956. However, he turns 30 in the episode The Big Three-O (S1E11), which aired on December 11th, 1987, which he means the character was born in 1957.