If dark matter was created in the early universe and its formation released energy, is there any evidence of that energy in the cmb? When atomic nuclei fuse, energy is released. Is there anything about the CMB energy distribution that suggests that dark matter could have formed from other particles that released energy?
 A: Please feel free to specify your question further in case I'm not hitting your nail with my answer-hammer.
How (and when) dark matter formed is an open question and depend on the particular dark matter model that is invoked. For a broad class of models called "thermal relic particles", dark matter was in equilibrium with the primordial thermal bath. Thus, dark matter particles and "normal matter" constantly annihilated, into each other, and back and forth. In that sense there are many models where "dark matter formed from other particles that released energy".
The CMB is emitted some 300,000 years after the Big Bang. At that point, dark matter already exists in abundance; in fact, we expect that it formed less than a minute after the Big Bang. Thus, all that is left as a possible imprint in the CMB is the overall temperature of the thermal bath (the temperature of the universe) and one shouldn't expect any signature in the CMB from dark matter production or annihilation.
Taking this even further through the evolution of the universe, what is known from structure formation is that dark matter is non-relativistic ("cold"). That places limits on the amount of energy that can be pumped from our baryonic world into the dark sector.
A: This recent paper discusses the amount of energy that can be injected into the primordial plasma without excessively altering the cosmic microwave background (CMB) or the abundance of light elements emerging from primordial nucleosynthesis. The most stringent constraint comes from the deuterium abundance, which enforces that an entropy-injecting process occurring after nucleosynthesis ($\sim$ minutes) can contribute to the energy density at only the few-percent level without violating observational limits.
The CMB is also constraining, through limits on spectral distortions and on $N_\mathrm{eff}$ (the relative energy density of neutrinos), but its constraints are typically weaker.
We generally assume dark matter was created before nucleosynthesis. Energy injections that occur prior to about 1 second (the time of neutrino decoupling) have no impact on anything we observe.
However, it is possible for dark matter to form much later, even as late as tens of years ($z\sim 10^6$); see this paper. It must then form by a process, like decay, that does not add energy to the plasma.
