Tcl didn't play in that space, and to their credit I don't think the Tcl folks were willing to go there just to ride the buzz.
That's not entirely true. I don't recall the exact timeline, but there was a Tcl plugin for Netscape which could be viewed as playing in much the same space as Java or Flash. A bit of work on media display and animation, and it might well have taken the space that Flash came to dominate.
Unlike browser Java of the time, the Tcl plugin didn't try to bury itself deep within the roots of the browser, was fast, and worked. :>