AP in WandaVision ep. 5 (spoilers) 4 Months, 2 Weeks ago
In the third episode "Now in Color" (which felt like a 70s sitcom) Wanda finds herself pregnant. Throughout the episode (aka a day) she becomes more and more pregnant eventually giving birth to twins Billy and Tommy.
In the 5th episode "On a very special episode" (80s sitcom) Wanda and Vision are having typical new sitcom parent issues with the babies not sleeping and just crying. Their neighbor Agnes volunteers to watch them for them. They talk and when they go back to them. They are missing from their cribs. They hear the voice of children and turn around to see the twins have aged up to 5
Later in the episode Billy and Tommy find a dog (sitcom fashion) and try to prove they can take care of it. They are found out. Wanda and Vision say they are too young for a dog. They can have one maybe when they are 10. The boys grin and age up to 10 (visually instead off screen)
when the dog dies, Wanda tells them to not age up to make themselves better. "Cant brush off aging because its convenient"