I get it. The phrase 'look like the back end of a bus' means looking ugly.

我明白了。look like the back end of a bus这个短语的意思是看上去很丑。

And he wrote to his friends that he dumped me because I look like the back end of a bus.

他还写信给他的朋友们说是他甩了我，因为我长得太丑了。

So this expression, 'look like the back end of a bus' is not a very pretty thing to say to anyone.

所以这个表达对任何人来说都是不好的事情。

Well, you can't look like the back end of a bus when you go on TV, no matter what kind of TV programme it is.

你不能丑丑地上电视，无论是哪种节目。