Textbooks are crucial ELT resources for instructors and students to comprehend the subject being learned since they are filled with linguistic knowledge and cultural aspects. From the English as an International Language (EIL) perspective, English textbooks need to expose students to a variety of English language variations, including a variety of characters from different cultural backgrounds and a variety of cultural representations. This qualitative study employs a content analysis method to evaluate the extent to which the Get Smart Plus 4 textbook incorporates linguistic and cultural diversity. The research objective is to examine the textbook's content, including characters and language varieties, and assess its alignment with the goals of EIL and lingua-cultural dialogue. By analyzing the textbook's content, the study aims to identify the presence or absence of linguistic resources that implicitly display variation in English varieties. The findings reveal that while the textbook includes characters from various cultural and geographic origins, it tends to favour the inner circle form of English, thereby overlooking other English varieties. This absence of linguistic resources undermines the goal of EIL, which stresses the importance of lingua-cultural dialogue. These findings highlight the need for ELT materials to foster a broader range of English language variations to promote a more inclusive and culturally diverse learning environment.