Pound Cake and Pumpkin Cake

Pound Cake and Pumpkin Cake are Mr. and Mrs. Cake's fraternal twin foals who make their debut appearance in the episode Baby Cakes. They are fully voiced by Tabitha St. Germain and Andrea Libman.

Season two
The two are first introduced as newborn foals in the episode Baby Cakes, where the ponies visit them in the hospital. They are surprised to find out that Pound Cake is a male Pegasus and Pumpkin Cake a female unicorn, despite the fact that their parents are both Earth ponies. Mr. Cake explains by referring to distantly related unicorns and pegasus in his and Mrs. Cake's family trees. Rainbow Dash, Twilight Sparkle, and Rarity caution the Cakes that young unicorns can exhibit bursts of magical power and that young Pegasi can be quite a handful once they learn how to use their wings.

The next scene shows the toddlers playing with Pinkie Pie on what she calls their "monthiversary". Despite being only one month old, Pound Cake and Pumpkin Cake are already able to run around the house. This is true with young ponies in real life who are usually able to walk hours after being born. That same day, the Cakes are also in need of a babysitter, and after Twilight Sparkle, Applejack, Rainbow Dash, Rarity, and Fluttershy decline the offer, they reluctantly ask Pinkie Pie to take care of the foals while they deliver a catering order.

This proves more difficult and less fun than Pinkie had expected. Her attempts to calm the foals when their parents leave, including trying to feed or bathe them, all end with the babies crying. Each time Pinkie can calm them only by emptying a bag of flour over her head, which amuses the foals greatly, but is a huge pain for Pinkie, especially in one scene where Pinkie Pie attempts to give the two foals a bath, and, as a last resort, ends up dumping another bag of flour on top of her head. Pinkie has become very wet while trying to give the twins a bath, and the flour mixed with the water ends up creating a sticky, doughy mixture on top of Pinkie's head.

Later in Baby Cakes, they also prove the adult ponies' warnings from the beginning correct. Pound Cake makes it difficult for Pinkie to chase after him when he starts flying and walking on the ceiling with the help of his wings; and Pumpkin Cake uses unicorn magic to levitate herself, phase through a laundry basket Pinkie Pie has trapped the two under, and break chains Pinkie had locked a toy chest with.

Eventually, it is Pinkie Pie who breaks into tears when she realizes she cannot keep the foals under control. Only then do the babies stop playing around; they attempt to cheer Pinkie up by imitating what she did to amuse them - emptying a bag of flour over their heads. The next scene shows them peacefully sleeping in their crib, giving Pinkie the opportunity to clean up Sugarcube Corner before their parents come home.

Pound Cake displays a habit of pounding on things and Pumpkin Cake has a habit on chewing on objects that aren't food, including a table cloth, a towel, and several toys. She also tries to chew on a broom stick that Pinkie Pie uses. Pumpkin Cake is the first unicorn to be seen levitating herself, other unicorns haven't been seen using that ability. An exception being Twilight Sparkle levitating herself in The Crystal Empire, Part 2 and in Magical Mystery Cure.

Pound and Pumpkin Cake can fly and use magic, respectively. However, Scootaloo and Sweetie Belle have never used these abilities despite being years older, and the twins haven't been shown using their powers since Baby Cakes.

The foals say one word each in Baby Cakes, spoken by Andrea Libman and Tabitha St. Germain: Pound says "Pinkie", followed by Pumpkin saying "Pie".

Pound Cake and Pumpkin Cake make a brief appearance in the opening of the episode A Friend in Deed, watching Pinkie Pie do some sort of aerobic exercises. Initially unamused by Pinkie Pie's attempts to coax them into laughter, they become amused after Pinkie Pie manages to get into an accident, mirroring their behavior in Baby Cakes.

The twins appear briefly again in Ponyville Confidential, throwing a tantrum which is photographed and later featured in a "Gabby Gums" column of the Foal Free Press.

Season three
Pumpkin Cake, without her brother, makes another brief appearance in Magic Duel, sitting on a makeshift throne made by her parents, whom are enslaved by Trixie at the time.

During Magical Mystery Cure, Pound Cake appears in one of Pinkie Pie's flashbacks.

Comics
Larry's Comics and Jetpack Comics exclusive Covers RE of Friendship is Magic issue #5 depict 5-bit-denominated Equestria postage stamps that each feature Pound Cake or Pumpkin Cake.

Twilight Sparkle and the Crystal Heart Spell
Pumpkin Cake and Pound Cake appear in chapter 2 of the book Twilight Sparkle and the Crystal Heart Spell, "A Foal House". They say "Giddyup!"

Pound Cake

 * Baby Cakes
 * A Friend in Deed
 * Ponyville Confidential
 * Magical Mystery Cure (flashback only)

Pumpkin Cake

 * Baby Cakes
 * A Friend in Deed
 * Ponyville Confidential
 * Magic Duel

Merchandise
Pound Cake and Pumpkin Cake miniature collectibles are included in an upcoming character collection set.

Quotes

 * Baby Cakes
 * Pound Cake: Pinkie...
 * Pumpkin Cake: Pie...

"Giddyup!"

- Twilight Sparkle and the Crystal Heart Spell