If someone were to compile a book called The Wit and Wisdom of St. Thomas Aquinas, he would probably spend a lot more time working on the wisdom part than the wit part. Whatever might be said for him, St. Thomas was not known for his playful banter.
In fact, one story told of him suggests more killjoy than wit. It seems some fellow students in a playful mood called to Brother Thomas as he labored at his studies, "Brother Thomas, come quick! There's a cow flying in the field!"
St. Thomas made his way to the window, at which point the friars began to laugh at him. He answered, "I would rather believe a cow could fly than that a friar would lie."
It's hard to know how seriously to take this story. Maybe we should just say turning a practical joke into an illustration of the virtue of truth is the sort of thing he might have done, and leave it at that.
But I shouldn't leave that term "killjoy" unchallenged. Per the story, Br. Thomas wasn't killing joy, but mirth at another's expense. As he would write years later:
Jesting implies nothing contrary to charity in relation to the person with whom one jests, but it may imply something against charity in relation to the person who is the object of the jest, on account of contempt....
If indeed he managed to kill anything with his remark, it wasn't the effect of charity called joy.
For that matter, if the story of the flying cow were told, mutatis mutandi, about Samuel Johnson -- which, for all I know, it has been -- it would be received as a clever and cutting riposte.