It is funny, I didn't even know a company like Build a Bear was publicly traded. I remember these stores in the malls when I was in junior high. They went through a very long stretch of difficult operations, talking more than 15~ years.
My main fear here, at least after reading what is driving the stock, is "fad" type conditions. From the knowledge that I have, this company is tapping into the nostalgia factor in regards to aggressive marketing to individuals my age that would have utilized these stores when they were children.
Nostalgia tends to be cyclical. What’s “cool” now might lose its appeal once it becomes overexposed or once consumer tastes shift. I have difficulty investing in companies that are riding any sort of consumer "wave", and I do think they tend to fade away. For example, if the millennial generation loses its taste in these products, I don't think it has a large enough audience to tap into otherwise to sustain revenue.
I just have a difficult time believing this one will keep the momentum up over the long-term. Short term, it could be a solid play on some substantial momentum.
For Groupe Dynamite, I believe they are a more "fast fashion" type company than Aritzia. What I mean by fast fashion is they're quickly copying current fashion trends, pushing out large scale amounts of clothing, and repeating the cycle when that fad falls out of favor. Aritzia has much longer product cycles, resulting in lower inventory turnover, less R&D, etc.
Something like Groupe Dynamite which mass produces cheaper clothing can gain momentum during cycles where consumers aren't spending much. However, I'd view Aritzia as much stickier.
Again, I think you have two solid companies that can ride short-term momentum and produce some solid returns. But I have difficulty completely a long-term thesis for either of them.