“Pre-trained Language Models (PLMs), as parametric-based eager learners, have become thede-facto choice for current paradigms of Natural Language Processing (NLP). In contrast, k-Nearest-Neighbor (k-NN) classifiers, as the lazy learning paradigm, tend to mitigate over-fittingand isolated noise. In this paper, we revisit k-NN classifiers for augmenting the PLMs-based clas-sifiers. From the methodological level, we propose to adopt k-NN with textual representationsof PLMs in two steps: (1) Utilize k-NN as prior knowledge to calibrate the training process.(2) Linearly interpolate the probability distribution predicted by k-NN with that of the PLMs’classifier. At the heart of our approach is the implementation of k-NN-calibrated training, whichtreats predicted results as indicators for easy versus hard examples during the training process. From the perspective of the diversity of application scenarios, we conduct extensive experimentson fine-tuning, prompt-tuning paradigms and zero-shot, few-shot and fully-supervised settings,respectively, across eight diverse end-tasks. We hope our exploration will encourage the commu-nity to revisit the power of classical methods for efficient NLP1.”