The Toaster in The Sink was ordered to go offline when Dr. Mobius left the Think Tank. His personality back-up is recovered from a "toaster altar" in The Cuckoo's Nest. The Toaster is psychotically violent, aggressive and megalomaniacal, bent on destroying the Earth with atomic fire. However, he is unaware atomic fire has already rained when the Great War began. When informed that the Earth has already been destroyed, the wind is somewhat taken out of his sails, albeit briefly, before he quickly returns to his "Burn the World" agenda by threatening to bathe the world in "atomic fire....again."
All My Friends Have Off Switches: The Toaster is one of the appliances that the Courier must retrieve a module for. The module is found in The Cuckoo's Nest, sitting on what appears to be a shrine for toasters and electric appliances.
If the Courier lies, claiming that his prior statement that the world had already been incinerated in an atomic fire was "just a joke," Toaster will be relieved that he "isn't as redundant and useless as Muggy."
If the Courier has good or neutral Karma, the ending slide show of Old World Blues relates that the Toaster continued to rant about how he would burn the world. After a particularly violent episode, the other appliances got tired of the Toaster and dumped him into a bathtub. In his last moments, the Toaster swears that they would "rue the day when they had bread... and no way to toast it."
If the Courier has evil Karma, then the ending slide show shows that the Toaster, learning from the Courier, continued destroying appliances and eventually built a shrine to itself in The Cuckoo's Nest.
Despite having to be informed of the world's destruction, he apparently knows full well about Caesar's Legion and the NCR without any prior information.
Even if the Courier is not carrying any toasters, but has other small appliances or Saturnite fists on their person, the option of saying, "I've got some toasters for you" will still appear. Selecting this dialogue option will open the Toaster's interface.
The Toaster is the only Sink personality that additional upgrades can't be found for.