互联网的发展推动了语言生成、传播和使用方式的持续变化，网络空间中不断涌现突破传统词语搭配和语义规范的新型表达。“你胆子真是肥嘟嘟的”以“胆子真肥”为基础，通过“肥”与“肥嘟嘟”的替换形成非常规语义搭配，并在网络传播中获得新的语用和社会意义。本文从社会语言学视角出发，采用个案分析和语境分析的方法，考察该表达的语言形式、语义特点、语体特征、语用功能及形成原因。研究发现，该表达通过语义错位和形式仿拟突破常规搭配，同时借助“肥嘟嘟”的可爱化色彩弱化原有表达的责备意味，呈现出幽默、戏谑、亲昵和娱乐等特点，实现“狠话软说”的表达效果。其流行与网络交际的非正式化、娱乐化和互动性密切相关，也体现了语言使用者的求新心理和群体认同需求。本文认为，该表达的产生与传播是语言创新、社会心理和网络文化共同作用的结果，体现了网络流行语在社会交往和文化表达中的重要作用。

The development of the Internet has continuously transformed the ways in which language is produced, disseminated, and used. Novel expressions that depart from conventional collocations and semantic norms have emerged widely in online communication. The expression “Ni danzi zhenshi feidudude” is based on an established colloquial expression meaning “you are really bold.” By replacing the original adjective with a reduplicated and affectionate form meaning “chubby,” it creates an unconventional semantic combination and acquires new pragmatic and social meanings through online circulation. From a sociolinguistic perspective, this study employs case and contextual analyses to examine the expression in terms of its linguistic form, semantic characteristics, stylistic features, pragmatic functions, and underlying causes. The findings show that the expression breaks conventional collocational patterns through semantic incongruity and formal analogy while using the affectionate connotations of the new form to soften the critical force of the original expression. As a result, it conveys humorous, playful, teasing, intimate, and entertaining meanings, producing a pragmatic effect of expressing harsh remarks in a softened manner. Its popularity is closely related to the informality, entertainment orientation, and interactivity of online communication, while also reflecting language users’ desire for novelty and their need for group identification. This study argues that the emergence and dissemination of this expression result from the interaction of linguistic innovation, social psychology, and online culture, demonstrating the important role of Internet catchphrases in contemporary social interaction and cultural expression.