小丑大部分都是贬义的，如果一个小丑以滑稽的动作逗别人开心，我觉得就没有太多贬义了，但 clown 更多用来形容言行举止不恰当的人。class clown 意为“班级小丑，班级活宝”，寓意：
a wiseacre
自以为是的人
someone who stands out in a class because he makes constant jokes and pokes fun at people
在班上脱颖而出的人，因为他经常开玩笑和取笑别人
a student who is funny and uses his wit to make others laugh
一个有趣的学生，他用自己的智慧使别人发笑
解析：make sb do sth 表示使某人做某事，宾语后面接不带 to 不定式。
例如：
He is the class clown with the constant talking and making fun of others.
他是班上的小丑，总是喋喋不休，取笑别人。
解析：make fun of sb 表示嘲笑某人。
Your father doesn't always look like it but he was quite a class clown in his days.
你父亲不总是这样，但他那时候是个十足的小丑。
A class clown makes fun of people but should be sporting enough to be able to laugh at himself.
一个班上的小丑取笑别人，但应该有足够的高尚，能够笑自己。
解析：be able to 强调通过努力而获得的能力。
It was shocking to see him so serious after the results. Otherwise he is such a class clown.
结果出来后，他如此严肃，真令人震惊。否则他就是个班里的小丑。
It seems to be the responsibility of the class clown to cheer everyone up after some bad moments. You in particular are very good at it.
似乎班上小丑的责任是让每个人在经历了一些不好的时刻后都振作起来。你尤其擅长这个。
解析：不定式 to cheer everyone up 是句中真正的主语，它有自己的逻辑主语 the class clown，可以改为：
To cheer everyone up is the responsibility of the class clown.