In the sequel, the entire scene where Gloria sings "Bridge of Light" to Erik. It gets better when the other penguins join in.
It gets more Heartwarming at the end when Erik joins in.
Erik singing an improvised opera about how heroic and brave his father is to convince the elephant seals to help the penguins, and it works.
Everyone trying to help each other out from being trapped to the song Under Pressure.
Even the penguins who are trapped help by singing and encouraging the penguins and elephant seals who are pounding on the ice.
Erik dancing on Mumble's feet near the beginning. Sure, it goes wrong less than a minute later, but the sheer joy on his face is wonderful to see.
In the first film, the Amigos just accept Mumble as one of their own, no questions asked, and they stick by him all through both films. Fast and true friends, indeed.
In the first movie, the slow, building scene after it looks like Gloria is rejecting Mumble for the final time... and then in desperation he finally stops trying to be pretending to be something he's not and begins to dance without holding back... and they both realize that his rhythm matches Gloria's heartsong.