Recent investigations have shown that different topographies in polyethylene (PE) lead to either thermorheological simplicity (linear and short-chain branched PE) or two different types of thermorheologically complex behavior. Low-density polyethylene (LDPE) has a thermorheological complexity, which can be eliminated by a modulus shift, while long-chain branched metallocene PE (LCB-mPE) has a temperature dependent shape of the spectrum and thus a total failure of the time-temperature superposition principle. The reason for that behavior lies in the different relaxation times of linear and long-chain branched chains, present in LCB-mPE. The origin of the thermorheological complexity of LDPE might be the temperature dependence of the miscibility of the different molar mass fractions that differ in their content of short chain branches.