The properties of polymer blends depend upon the morphology of the dispersed phase. The morphology where the dispersed phase exists as high aspect-ratio fibrils is important because the fibrils can form entanglements and contribute substantially to the viscoelasticity of the polymeric host. In this study we compare the rheological and thermal properties of metallocene catalysed polyethylene (mPE) with that of mPE containing fibrillated polypropylene domains (mPE/fibrillated-PP) and mPE containing spherical PP domains (mPE/spherical-PP) and correlate the results with the foaming behavior of the materials. Rheological analysis reveals enhanced elasticity in mPE/fibrillated-PP which we attribute to the formation of an entangled network of fibrils in the melt. This network of entangled fibrils results in marked strain hardening in uniaxial extensional flow, as well as shear thickening responses in shear flow. Such rheological responses are not observed for mPE or mPE/spherical-PP. Oscillatory shear flow investigation of the isothermal melt crystallization of the samples reveals a two orders of magnitude decrease in the time for the onset of crystallization in the mPE/fibrillated-PP and a one order decrease in the time for the onset of crystallization in the mPE/spherical-PP relative to neat mPE. Strain-induced hardening and improved crystallization kinetics are indispensable for foam manufacturing. Results from foam processing experiments reveal that the mPE/fibrillated-PP shows up to a four orders of magnitude increase in the number of bubbles per unit volume compared to neat mPE.