No, I think this is a really silly idea. Let's assume that students are trying to get a 100% score. What is the correct answer to "I love mathematics - true/false"?
Is the "I" there the teacher? The student? If it is the student what is demonstrably the correct answer? How can the teacher marking the exam possibly know if the student loves mathematics or not? (The student might hate it, but be doing it because it is a course prerequisite).
Since there is no answer that can be shown to be correct, then the student has to guess "what am I supposed to say here?". Whatever answer they guess, if they are wrong, they won't get a top mark for the paper.
Now you might say "I'll accept any answer and mark it correct". But the student will have wasted time on the question, trying to work out what it means, and therefore having less time to spend on genuine questions.
Some students might try to read the question as a riddle or puzzle. For example, "I" = 9, "L" = 12, "O" = 15 and so on, and then try to work out what that means mathematically.
As an example of why this can fail, see this article about a VCE (year 12) exam held in Australia in 2012. A history exam paper inadvertently had a giant robot on the artwork Storming the Winter Palace by Nikolai Kochergin.

Students complained that they wasted time trying to work out the significance of the robot, for example:
I went through a thought process something like this, 'What's that thing? It's definitely a robot. But it's on my history exam, so it's not a robot. But it can't be anything else. LOOK AT THOSE GUNS!' I stared at the image long and hard. It was extremely off-putting because you just don't expect there to be a mistake on your exam, especially one like that.'
Don't do it. It might be a fun game to you, but for the students this is an off-putting, time-wasting exercise that could well cause them to do more badly on the exam than they might otherwise have, and then subsequently complain.
In the case of the Australian exam the assessment authority had to apologise afterwards for any impact that the image might have had on students completing the exam. And in their case it wasn't even intentional!
Indeed, the authority had to adjust the scores for 130 students over the confusion about the robot.
Dave L Renfro said:
I sometimes had students answer my 1+1=−−− question (see my answer) with things like 10(in base 2),
Yes, I didn't want to bring that up, but see Quotations by Bertrand Russell:
"But," you might say, "none of this shakes my belief that 2 and 2 are 4." You are quite right, except in marginal cases -- and it is only in marginal cases that you are doubtful whether a certain animal is a dog or a certain length is less than a meter. Two must be two of something, and the proposition "2 and 2 are 4" is useless unless it can be applied. Two dogs and two dogs are certainly four dogs, but cases arise in which you are doubtful whether two of them are dogs. "Well, at any rate there are four animals," you may say. But there are microorganisms concerning which it is doubtful whether they are animals or plants. "Well, then living organisms," you say. But there are things of which it is doubtful whether they are living organisms or not. You will be driven into saying: "Two entities and two entities are four entities." When you have told me what you mean by "entity," we will resume the argument.
Thus, even a "simple" question about what is "1+1" could have arguably difficult answers.
Another issue is, by making joke questions you are treating the exam as a joke. That is, it is trivializing the experience. Some students may have studied long and hard, and have expectations from their parents that they do well. To have jokes introduced into the exam appears to say that the examination is being trivialized.
This question is out of the domain of the subject. Asking a question about a state of mind ("do you like something?") is more appropriate in, say, psychology. It isn't a calculus question and is therefore inappropriate. For example, if you asked "How do you boil a hard-boiled egg?" people may well object that this is not a relevant question in a calculus exam, even if they knew how to boil eggs.
Adding in questions that (assuming the reader can tell are a joke) alters the effective score in the exam. Let's say your joke questions are worth 5%. That means that:
- Someone can get 5% in Calculus even knowing nothing about the subject; and
- The other answers are scaled in value. For example a question which claims to be worth 10% of the score is really 10% of 95 and not 10% of 100, altering what the question is really worth.
Having joke questions, which are intended for everyone to get right unconditionally, could penalize a student who, because of time constraints, does not reach that question. They may say afterwards "if only I had known there was a 'free' 5% from answering questions 19 and 20 I would have answered them first".
You might respond "but I'll give everyone full marks for my joke questions even if they don't answer them" now makes the questions seem even sillier. An exam question that is always marked correct? Even if you don't answer it? What is the point of having it?