Being thoughts, this doesn't count as Linus' first words. I'm not even sure this counts as Linus' first thought balloons, but I can't find the strip in the archives in which he complains about "big kids," which is the prior use I remember so maybe that comes later. But I think it is the first example of Linus' voice really coming through clearly to the reader, even if it isn't audible to other characters.
Linus is interesting because we first get a few strips with him thinking before he actually starts talking. Sally also does this when she shows up. I think Rerun gets it too.
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