Belinda tickled him, she tickled him unmerciful,
Ink, Blink and Mustard, they rudely called him Percival,
They all sat laughing in the little red wagon
At the realio, trulio, cowardly dragon.

Belinda giggled till she shook the house,
And Blink said Weeck! which is giggling for a mouse,
Ink and Mustard rudely asked his age,
When Custard cried for a nice safe cage.
Custard, the dragon, was considered cowardly as he did not fit into the usual definitions and attributes given to a dragon. He did not want to destroy other people, nor did he want to exhibit his power to other people. We have fixed certain standards for what bravery is in society. When people or other beings do not stick to those particular standards, we tend to tease them. For example, when we see a man being vulnerable or letting out his emotions, we tend to tease him by asking about his manliness. This is because we have fixed certain stereotypes in our minds, and we cannot process that people can choose to behave or react in whatever way they want to. No rule that states how all creatures are supposed to behave. Just because dragons are generally brave and have a tough outer appearance, Custard need not necessarily be the same. He can be a scared dragon who wants to stay in his comfort zone.
Belinda loves teasing her pet dragon as he is unlike any dragon. It is usually tough when people we love make fun of us. But Belinda did not seem to care about it as she kept tickling him. Usually, no person dares to go near a dragon, let alone tickle it. But Custard, the simple and scared dragon he was, allows himself to be tickled mercilessly.
Along with Belinda, the other pets also join to make sure to tease him for being weak. They call him Percival. Percival was a knight in King Arthur’s court. He was very unattractive, so people assumed that he was fit for nothing. But the legend states that he was the one who later secured the holy grail, which is a cup that possessed magical abilities like retaining one’s youth and curing sickness. Custard is also judged based on his present characteristics, but Belinda and her pets do not seem to recognize that he can do a few other things.
Holy grail taken by Percival
They all sat there in the red wagon, making fun of Custard for being a coward and not being fierce like other dragons. According to them, he was a truly coward dragon. Belinda found it so amusing that she nearly shook the house with laughter. Blink the mouse laughed, and it sounded like the word week as his giggles left his mouth. Ink and Mustard liked to tease him more that they rudely asked him for his age, meaning if he was a little one. Only little kids are scared to do things, and they need to be in the comfort of their parents. Likewise, they ask him if he was a child to ask for a soft cage.
Words with difficult meanings:
TickledA light touch that causes mild discomfort
UnmercifulNot showing any pity
VulnerableA person who needs support physically or emotionally
CowardA person who is scared of everything
A light and silly laugh

National Council of Educational Research and Training (2006). Beehive. The Tale of Custard the Dragon - Ogden Nash (pp. 129-132). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.