The assumption in the question is mistaken.
As @Mithrandir already linked above, it's a common assumption of adult readers that Hobbes couldn't possibly be real but that's just not how the actual comic works .
Watterson intentionally left the entire issue unresolvable, with strips like this where Hobbes should need to be real for Calvin to be in the situation he's in.
The shift between how Calvin and his parents see the world is very real and part of what the comic explores, but Watterson didn't feel the parents were right and Calvin was wrong .
scifi.stackexchange.com/users/80732/lly
No.
Calvin's parents mostly play along with his belief Hobbes is real.
But when Susie directly points out that Hobbes is a stuffed toy, Calvin simply ignores her: In the very last panel of the comic, we see Calvin as convinced as ever that Hobbes is a real tiger:
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What makes you think that he's not real?
First, consider what you mean by "real.
" If you mean "could you put a video camera there and record Hobbes doing the things that the comic strip has him doing with Calvin?
", that's deliberately left ambiguous in the comic strips.
In fact, even in a strip where Calvin takes photographs of Hobbes, Calvin and his dad just see the pictures differently, so it resolves nothing
- it's not clear what the pictures "really" look like.
I'm not convinced that the "video-camera approach" is the best way to view this, though.
Try to view it through the characters' POV.
From Calvin's POV,
yeah, he's real.
From the other characters' POV, he's a stuffed tiger.
I don't think that it's really important (or provable from the comic strip)
which one is "correct" in the video camera sense.
scifi.stackexchange.com/users/77587/EJoshuaS - Reinstate Monica
As far as I understood when I read Calvin and Hobbes, the situations Calvin finds himself are always ambiguous.
One could choose to believe that Calvin just has a high imagination in his role play with his stuffed toy or one could believe that Hobbes is some kind of magical toy that comes to life only for Calvin and is a stuffed toy to the rest of them.
something like Perry in "Phineas and Ferb" (just the concept not the stuffed part).
And I always read these comics from the second point of view because it makes it that much more fun.
Especially since we never hear dialogues from Hobbes when there are other people around.
All his interactions are mostly done when they are alone.
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I'd argue yes, in this strip (May 20, 1986):
scifi.stackexchange.com/users/80922/Simon Zuckerbraun
In the comic strip  Calvin and Hobbes , was there any moment where Calvin realised that Hobbes wasn't real?
Did Calvin ever realise that Hobbes was not real?
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<comics><calvin-and-hobbes>
scifi.stackexchange.com/questions/156481
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It is something of an assumption to say that Hobbes is not real, and therefore, this question may indeed be mistaken. However, there is no indication at any point in the comic series that Calvin realises that Hobbes isn't a real tiger. The question misses the point because the stories are to some extent about what is real and how POV affects this and no final answer is provided.
The question makes an incorrect assumption that Hobbes is not real - whereas the comic itself never makes this clear, and that is the point of it. No - his parents mostly play along with it but when Susie points out Hobbes is a stuffed toy Calvin ignores her. It depends on what you mean by real, as this is a product of a character's POV. The situations are always ambiguous so it is never clear what is real and what is not.