In the episode where Buddy was making a cake for the 40th anniversary of Sesame Street, he also makes a three foot in diameter chocolate chip cookie for Cookie Monster. Cookie's big :O face is priceless.
Two more bits, thanks to Cookie Monster: Cookie's reaction when Buddy first reveals he's a baker and Buddy's "He (Cookie) is real" when Joey asks why he's making the giant cookie for a "puppet" as seriously as saying "I have black hair".
Related to that...
Elmo: This cake is going to take a long time to eat. Abby: Not with Cookie Monster around.
Hell, just the fact that the the actors are celebrating in character, as if kids were actually watching this.
Cookie Monster's reaction to the giant cookie cake. First, he stands there in shock with his mouth wide open, then immediately runs out with it, obviously intending to eat the whole thing himself.
Special mention also goes to the Bachelorette cake episode, when Mama Valastro accidentally gets a peek at the fully completed nude figure, resulting in a long, drawn-out scream.
There was a segment recently on Good Morning America, a silly one about one year old babies smashing their birthday cakes that was going to have a competition between four babies to see who could make the biggest mess. Since it's put on this page, three guesses who shows up with the cakes he or his bakery made for the event. Made funnier because, when asked if he felt bad about his cakes getting destroyed by babies, Buddy actually expressed enjoyment and made it out that it was a requirement for any baby's first birthday. The cherry on top is that, when the babies are allowed to have at it, they barely did anything, with one not even wanting to touch the cake. Epically funny, admittedly not from Cake Boss but not something that would've been out of place on that show.