Title text: The chemistry experiment had me figuratively -- and then shortly thereafter literally -- glued to my seat.
The adverb "literally" implies that the action it describes actually happened, while its opposite, "figuratively", is used when the action it describes is being used as a figure of speech, and is not a representation of what actually happened. However, "literally" is often used colloquially to mean "really" or "very", and even though Merriam-Webster says it is a perfectly fine (if not correct) use of the word, a lot of people object to this usage.
In this comic, one of the two people (we'll call him Cueball for now) accidentally mentions he was literally glued to his seat (one could easily assume that they had just left a theater), at which point a crazy man off-panel loudly corrects him. The crazy man mentions that he has been stalking Cueball for eighteen years since an incident in seventh grade, where the crazy man (as a kid) incorrectly uses "literally" and young Cueball corrects him. He felt humiliated, overreacting to young Cueball's simple correction, and began to follow Cueball everywhere, vowing to be present when he makes the same mistake the crazy man had made in seventh grade.
When Cueball tells him that he is "literally the craziest person" he's ever met, the crazy man thinks that he incorrectly used the word "literally" again; however, Cueball reassures him that he did not misuse it, meaning that the crazy man actually is the craziest person he has ever met.
The title text points out that a chemistry experiment gone wrong is one of the few things that could cause someone to literally be glued to their seat, having previously been figuratively glued to their seat in fascination.
The title text could thus also be understood as an explanation of how the sentence which was interrupted would have ended: I was literally glued to my seat through the entire chemistry experiment.
In this case the crazy person did not even catch Cueball in making the error - and because he interrupted too soon and gave himself away he has lost the chance to do so ever. Even though he stalks Cueball, he may not have been able to join his chemistry class to witness the glue accident - and may thus, as described above, wrongly believe that Cueball was talking about a theater experience.
- [Cueball and a friend walking together. Cueball turns to the friend.]
- Cueball: I was literally glued to my seat through the entire-
- Crazy man [off-panel]: HAH! You mean "figuratively"!
- [Crazy man walks into the panel. He has messy hair and a messy beard. The other people stop walking.]
- Cueball: Who are you?
- Crazy man: Eighteen years I've watched you! Waiting!
- Crazy man: Ever since that day in seventh grade when you humiliated me.
- [Short flashback panel. 4 kids are standing around talking to each other.]
- Kid #2 [Crazy man]: I told him and he literally exploded!
- Cueball: Uh, unless he physically burst, you mean "figuratively".
- Hairy: Hah.
- Crazy man [outside of flashback panel]: Remember?
- Crazy man: I knew one day you'd slip, and I vowed I'd be there to see you fall. How does it feel?
- Cueball: You are literally the craziest person I've ever met.
- Crazy man: You did it again!
- Cueball: No, I didn't.