This case study explores how Swedish upper secondary students communicate in English as part of second language learning, in a blog shared with Thai students. Grounded in a sociocultural perspective on learning, the notions of Goffman's "frame shifting" and Bakhtin's concept of "carnival" are employed to analyse two specific students' negotiations and co-construction of postings in relation to authorship and audience. The findings show that when encountering a task introduced as part of schooling but contextualized in social media, the two students struggle to come to grips with how to frame the task. Initially, they frame the activity in relation to what counts as conventional language-learning practices but shift framing as they discover that other classmates' postings are framed more in line with social media contexts, distinguished by a carnivalesque spontaneous writing. Thus, for the two specific students who author the postings, the local audience consisting of their classmates plays the most significant role.