Apart from putting on elaborate parties, we usually create interesting cakes to go with them. Herewith, a retrospective.
It started simply, with your basic store-bought cake with a few toys stuck on top:

But that didn’t seem quite enough, so next time we took a store-bought cake and plopped a homemade cake on top of it! (That duck is all cake. Mmm.)

I wasn’t too happy with the next effort:

…so we supplemented it with another store-bought cake, though you can see our decorations becoming more elaborate (those “rocks” are chocolate, mmm):

Our first proper theme was for Archer’s “Mr. Sunshine” party. Here’s the cake:
Jonah chose a “peace” theme for his third birthday — we were so proud! This cake is in the shape of a peace symbol, with berries filling the voids in the shape.
Archer’s next party was all about superheroes. We made a cake to look like the yellow A on his notional red “Archer-man” costume.
Next Jonah had a Peter Pan party. (The candles are supposed to make the shape of a teepee.)
For Archer’s next birthday he wanted a “monkey in the jungle” party.

Then Jonah had his Yellow Submarine party. (The cake’s in the background of this photo, with the yellow submarine on top.)

Archer then had a “put on a happy face” party.

And Jonah had his Scooby-Doo party. It was back to a store-bought cake (with our own decorations) for this one.
Another store-bought cake for Jonah’s Star Trek party.

…and also for Archer’s vaguely sea-themed party:

Archer’s ninja-monkey cake was a joint venture between us and Expedition Island:

…but Jonah’s four Avatar: The Last Airbender cakes (air, water, fire, earth) were all us: