Within the domain of creativity, a significant challenge arises concerning inadvertent plagiarism, where individuals believe they have created a novel and original product, yet in fact unwittingly incorporate elements from earlier sources. Specifically, it remains unclear how this phenomenon relates to insight, particularly whether the aha-experience might accompany the generation of ideas which are actually recollections of previously encountered information, thus reflecting source-monitoring errors. The current experimental study aimed to test the hypothesis that during independent generation of verbal puzzles, participants would borrow ideas from puzzles, they had previously solved, thus demonstrating the phenomenon of inadvertent plagiarism. Additionally, it was investigated, whether the generation of ideas with borrowings would occur more frequently with insight and be accompanied by an aha-experience, due to their higher retrieval fluency. The study involved 48 volunteers. The procedure consisted of two stages. At first, participants were presented with remote associate tasks and attempted to solve them. One week later, in the second stage participants were asked to generate new verbal puzzle problems using provided solution words, half of which they had already encountered during the first phase, whereas the other half were new. The results demonstrated that the proportion of borrowing in the experimental condition, i.e., generating verbal puzzles corresponding to familiar solution words, significantly exceeded chance level, thus being evidence of inadvertent plagiarism. However, neither the reported instances of insight nor the ratings of aha-experiences differed significantly between the generation of verbal puzzles involving borrowings and the generation of completely new ones. These findings contribute to existing theories of inadvertent plagiarism and suggest directions for integrating research on insight, plagiarism, and creativity.